Below is my personal, blunt, honest comparison of drawing mediums (I buy all the art supplies myself and don't profit from writing positive reviews). It's mainly a summary for myself so that I won't splurge on art supplies which I don't need in the future, but maybe it can be useful for other people as well.
Good for fanart:
0) The good old pencil and charcoal are things which every beginner should have tried, so I'm not going dwell on them. I love both and they're great for sketches and detailed drawings. The same applies to black&white drawing inks with sable brush and pen.
1) Digital is forgiving if one remembers to save and backup, but it's also the most frustrating medium when one encounters problems and bugs one can't control.
Drawing and inking digitally is (at least to me) much more difficult than drawing and inking with a normal pencil or pen or brush. Even with the iPad and the Apple pencil (my current choice of tablet&pen), which makes the eye-hand coordination easier than an Intuos tablet does, it feels less good than a real pencil due to the glossy screen. I haven't ever tried out a Cintiq.
It's difficult for me to stay motivated when I draw digitally despite the many possibilities Autodesk Sketchbook offers because the tactile experience of colouring digitally is nothing compared to the tactile experience of colouring with traditional mediums. But I can get accustomed to digital colouring since zooming in makes painting details a snap (the zooming-in feature beats even the undo feature!). The perspective grid in apps like ibisPaintX can also be extremely useful.
One great disadvantage of digital colouring is the screen. My eyes will get tired much faster whenever I colour digitally.
I still have a lot to learn since I've only treated the pens and airbrushes in Sketchbook like a traditional medium until now, but it's cheap for people who already have an iPad and great for illustrations and fanart which one shares online since the preliminary sketches can be done on inexpensive drawing paper and it's easy to share the finished drawing (one can also share directly from the drawing app).
2) Copic markers look great on marker or manga paper (I prefer manga paper) and are fun to use but also smell (some people love the scent but it's hazardous, so one had better not sniff them regularly if one values one's health). They force one to be fast and accurate while blending, and they're generally extremely unforgiving, which is often an advantage if you want to be fast.
The clicking sound the caps make can be annoying to others (especially if you like to colour at night). The colours also look crappy after scanning, so I usually only take a photo, enhance the colours of the scan digitally, or add another layer of colour in a digital drawing app like Autodesk Sketchbook. Copics usually only look good with less than four layers (which is, again, an advantage when it comes to speed). Copic markers are great for drawings which need to be finished in one session.
The paper quality is important when one uses Copics so that it takes a few experiments to find out which paper brand one prefers. The markers are expensive (very expensive if you buy them separately) but refillable, which is good for (fan)artists who often work with them. Copics aren't lightfast, so the drawings need to be protected from sunlight and fade with time. One great disadvantage is also the price: you need many Copic markers (and many of the same colour) for them to look great, and I personally think that they're only good for the people who instantly fall in love with marker illustrations, prefer using real markers to a tablet, and want the Copics at any cost. For people who own an iPad and don't mind colouring digitally, it's much cheaper to use Autodesk Sketchbook since Sketchbook has a Copic palette.
3) Faber Castell Pitt artist pen (ink pens) have a brush nip and contain lightfast inks, in contrast to the Copics. But they're only available in bold colours and very few pastel colours (the pastel ones are often not pale enough for subtle details), and they don't blend as well. They're great for miniature sketches which aren't supposed to be realistic since they're cheap, small, light, and clean (also: lightfast!). You can also use them in colouring books (I've bought a few books but somehow I can't find the motivation to colour more than one or two pages and only use them to try out colour schemes).
4) Colour pencil drawings look almost as terrible as Copics when scanned and need to be enhanced or photographed unless one scans a very large pic and scales it down afterwards. Sometimes colour pencils (especially the pigmented ones for artists) smell (I'm slightly allergic to certain pigments, which I always notice when I use colour pencils). They're great for people who've just begun to try out all sorts of drawing/painting styles since they're less expensive than watercolour and Copics (especially since one needs less colours for them for a decent drawing). If you buy many artist-grade colour pencils (for example for realistic drawings), they're much more expensive than watercolours but still cheaper than Copics. They're also easy to use and forgiving because one can apply the colour slowly, with a gentle touch so that one can use the eraser in some instances. In the long run, the slowness, the danger of smudging the colours and getting a repetitive strain injury (no matter how light one's pressure is, the amount of movements the wrist has to make will put a strain on it with time) can spoil the fun.
Colour pencils are great for colouring books and sketching from life since they're light to carry, can be easily blended, and are versatile enough to be used for many different drawing styles. Realism and photorealism are easier with coloured pencils (you can plan all the colours in advance since you don't need to mix colours and the colours you get after layering are always the same).
I personally don't like using colour pencils for fanart, but they often look great when they're combined with Copics and only used for textures. (My favourite colour pencils are Caran d'Ache Luminance since they're usually very soft, but I love Faber Castell as well.)
I don't like water-soluble colour pencils, which are neither as good as non-water-soluble colour pencils nor real watercolours, but some people like the effects one can get by using them with water. The same applies to watercolour crayons or water-soluble pastels.
5) Watercolour often has the special watercolour look (even when you use a dry brush technique!), especially after scanning, which can be an advantage if one loves the look but also a disadvantage since it can be distracting in fanarts. The fun often depends on the quality of the brush (the feeling of a good sable brush on watercolour paper is hard to beat). I love watercolours for the same reason I love Copics: one doesn't need any pressure to apply it. Watercolour is also rather forgiving since mistakes can sometimes be removed or rubbed/washed out with a paper tissue and water. One doesn't need to be extremely fast although watercolour requires good planning.
Watercolour paints don't smell, don't make any noise, and are generally great unless one uses cheap watercolours, which fade too fast and look depressing. (Using a bad brush is even worse.) Good paper is even more important. Watercolour is good for artists who like to have few things of good quality (you only need a few good brushes, a few pans or tubes of good watercolour paint, good watercolour paper, and water).
Watercolour is a slow medium if you want to apply many layers since the watercolour layer needs to dry first. Impatience will immediately be punished, but you can apply many layers on heavy watercolour paper if you let them dry thoroughly. Watercolour is my choice of painting medium for original art and illustration (since I don't have a studio where I can paint with oils) although I prefer Copics and digital for fanart.
6) I've tried to like coloured drawing inks since I love black and white drawing inks and coloured writing inks. And while they look radiant on smooth watercolour paper, I don't really enjoy using them. More than two layers make the inks look dull, and less than two makes them look flat, so my general rule is to use exactly two layers of colour with them. They're unforgiving (one wrong stroke and you will have to live with the consequences), so you need to plan the drawing well. My main issue with coloured inks is that they are not lightfast and that I prefer Copics when it comes to non-lightfast ink drawings. They also have a shine to them which I don't like (but I must admit I've only used the Winsor&Newton drawing inks and other inks might behave differently). But they're great for calligraphy and for doing illustrations with bold, clean colours.
Coloured drawing inks dry out if you store them for years, so I'm trying to use up my inks and am not going to buy more in the future. All in all, drawing inks should be bought in small batches (especially black and white inks, which are usually lightfast) and be used up as fast as possible since the quality worsens after the bottle has been opened. It's almost impossible to screw on the caps so well that nothing happens with the ink.
Not good for fanart:
1) Pastels should be used in a studio with an air purifier or outside since the dust can ruin one's lungs with time (especially since a few pigments are slightly hazardous or even toxic). The fixative is also toxic and extremely unpleasant. It's difficult to draw details with them, so they're better for large paintings and drawings (there are pastel pencils and hard pastels for details, but they have to be applied in many layers to compete with the radiance of soft pastels), and soft pastels are so expensive that few people choose pastels for fanart (pastel pencils are better for this purpose but they easily break, which makes them very expensive to use, and you often can get the same effects more easily with coloured pencils in fanarts). Pastels are the best medium for plein air sketching, though, if you have many of them and are sketching at a place where the dust isn't an issue. And the colours are pure and brilliant, great for layering. (In fact, layering depends on the surface, and you can apply tons of layers on sandy pastel paper or pastel ground.) They are great for painters who like to be fast and need immediate results. Good luck for transporting the painting since half of it can fall off unless you've used a fixative, which darkens the colours a bit so that many painters prefer not to use it for the last layer.
2) Oil pastels don't have the dust problem but often need turpentine or mineral spirits to be blended. It's harder to paint details with them, and I don't like them for fanarts because they can be sticky and don't look good on small paintings. They're great for large sketches since they're cheap and it's very easy to paint with them (painting with them feels almost like doing finger painting). I enjoy painting with oil pastels but prefer soft pastels and oil paints.
3) I hate acrylics with passion! I've tested the best acrylics brands (my favourite are Golden, especially Golden fluid, and Atelier Interactive) and they're bearable enough but still ruin the brushes (Atelier Interactive wins since it's less rough to sable brushes), darken after drying, and look crappy in the first layers (again Atelier Interactive wins since the first layer with them looks less like plastics). Expensive acrylics paints is supposed to feel like butter (that's the word the ads usually use). Well, I've never use butter to paint but I can imagine that it would feel better than acrylics does. It's said to be much better for one's health than oils, which I really doubt since I can't tolerate the formaldehyde. Acrylics are also susceptible to mould and smell bad if you haven't used them for a long time.
The good thing about acrylics is that one can paint almost everything with it. It sticks to almost anything if one uses the right acrylics mediums and gessos, can be used for almost everything, and can look great in the end after varnishing. It's great if you like abstract painting and experimenting and enjoy how the many acrylics mediums behave and how the paint flows. I've used it as a replacement for oils in the last years. But since I like details and value my brushes and painting with acrylics makes me feel frustrated and sick (the results were good but the painting process was always painful), I've stopped buying acrylics.
4) Painting with oils is great as long as one takes care of one's health (or belongs to the few people who are totally unfazed by natural oils and solvents), opens the window, and doesn't sleep in the same room as the painting (I once did this for a week while a painting with cobalt blue and cadmium yellow was drying, and I wouldn't recommend this to anyone!). I can't imagine why anyone would want to use oils for fanart since it's so expensive and slow-drying, but it's great for original art. (If you want to take a photo, you should do it before varnishing because the gloss will ruin the photo). It's also probably the most forgiving medium apart from digital art since you can simply wipe away your mistakes as long as it's wet (and oils stay wet for a long time unless you mix fast-drying mediums into your paints). Oil paints are also expensive but last long if you take care to close the lid.
Oil paints are great for people who have a studio or a painting space at home, can use solvents without developing allergies or asthma (either because they're extremely tough or extremely careful), and like to paint in long painting sessions (keeping a whole day or at least half of the day free for painting). There are solvents like Gamsol which are supposed to be non-hazardous (which I haven't tried yet), but I've gone through bad times with watersoluble oils and acrylics mediums, both of which were supposed to be non-hazardous but made me sick or gave me rashes, so I'll be more careful in the future when it comes to modern painting mediums in general. (Don't ever trust the advertisements! XD)
If you like details, glazes, and layers, you need many good sable brushes unless you want to clean your brush all the time, and the painting surfaces are usually expensive as well so that it might be cheaper to start with miniatures and tiny brushes. If I were a professional artist, I'd choose oils for most of my paintings since it's so extremely satisfying to paint with them. You need to study the technique first and experiment a lot, but they don't cause stress since they let you paint slowly and push the paint around. It feels great to paint with real brushes on real wood or canvas. Also, they have a depth which is hard to imitate even with watercolours and colour pencils (and you need more layers of acrylics to get the depth of oils).
5) Watersoluble oils don't feel like real oils and can't be painted in the same way (if you use them like oil paints, they feel like cheap oil paints), and they're absolutely not my cup of tea although I admit that the results can look great (as much as I dislike acrylics, I'd prefer good acrylics paints to watersoluble oil paints). But there are people like Dag who can paint with watersoluble oils and like them as well.