Markers vs Watercolours
Same painting, different media. They are both based on this photo by Miss Souls StockI did a marker version and a watercolour version so I could compare the media: their advantages, limitations, and the overall finish.
This was copied from my original sketch on to marker paper. Marker paper is very thin, so it's easy to trace on to, but you need to make sure that you are drawing on the right side. This is because marker paper has one side that is more smooth than the other, which makes blending colours easier. I often have a hard time telling which side is which. You don't have to use marker paper, but it does make blending colours a little easier.
My original lines were drawn with a Micron 005. You need to use a light fast ink when colouring with Letraset or Copic markers, because I've found that certain types of ink smear when exposed to these markers. I like to draw a thin outline to begin with, then refine it when the colouring is over with.
I have a mixture of Letraset and Copic markers. They're both pretty good. The main advantage of copics is the smaller nibs and the fact that it is slightly easier to blend the inks together.
I think its easier to use markers on larger paintings, because even the small nibs are a little large, which can make detail work difficult. If you're careful, you can minimise mistakes. Some people use white acrylic ink to fix mistakes; this can be useful, but if you make a really big mistake, you are better off correcting it in photoshop. The clone stamp can be very useful in this regard.
The colours can be a little difficult to blend if you work slowly. Even using a colourless blender I had a had time making sure the shadows didn't look to stark. I used this tutorial by Ecthelian, where you colour in the dark shadows first and fill in lighter colours later. This works surprisingly well.
It can be difficult to create the exact shade you want using markers. It is possible to buy hundreds of shades, but they aren't cheap. You may have to compromise and settle for colours that don't perfectly match your subject.
It can also be difficult to create texture using markers. They tend to create a very smooth effect which might not be what you want. You can try stippling the colour, or using pencil colours or coloured ink on top of the marker.
Transferring your image on to watercolour paper can be difficult. I don't recommend sketching directly on to watercolour paper, because all the rubbing out can create pencil smears and may damage the paper. I usually copy the image on to tracing paper and scribble on the back of the tracing paper with pencil. Then i place the tracing paper over the watercolour paper and draw over the lines again.
Watercolour can be difficult to use. You have to learn how much water to add to the paint, and how long to allow it to dry. I recommend 'Animals in Watercolour' by Sally Michel and 'Mastering the Art of Watercolour' by Wendy Jelbert and Ian Sidaway, and Jenny Dolfen's tutorials.
It can be difficult to create intense colours with watercolour. i use Ecoline if I want a very intense shade, but be careful because the Ecoline can clash with the rest of your paints by looking too bright.
One big advantage of watercolours is that you don't need a lot of different colours. You can mix most of them out of a basic colour palette. The paints also tend to be cheaper than markers, depending on the brand you buy. I like Windsor and Newton, but I'm also using some random paints I got about 10 years ago, and even poster paint.
Another advantage that they have over markers is that they blend more easily. The finished painting looks more 'subtle' or 'soft' than a marker drawing. You may also be able to create more effects with them e.g. adding salt to wet paint creates a gorgeous blotchy effect, though I have heard that adding a little surgical spirit to markers with a cotton bud produces interesting results.
Unlike markers, you may find you have less portability when using watercolour. You need a container for water and a variety of brushes, and perhaps an easel. They can be great for working in pleine air, but you have to take into account the drying time.
So, to summarise:
Watercolours: cheaper, easier to blend, difficult to get very bright shades, drying time, different effect, softer finish
Markers: brighter colours, dry quickly, easier to transport and use, usually a bold finish but a skilled artist can create a more subtle look (like this)