I love them all <3 Oil is awesome, shadows blend so good and the painting itself looks wonderful, I really like oils, but I hate how much time they spend in drying and all the mess as well, you can't clean your pencils with just water, it's annoying to use thinner :/
Watercolors are my favorite, they kind of look like copic markers Which I love! But the problem is once you've painted you can't correct mistakes D: But watercoloring is my fav definetely even if I can't use them so well ~_~
Acrylics are good as well, they dry very fast, I don't use them so much, nor am I an acrylic fan
I love Water Colour personally beacause i havnt used oil much for myself, Water colour i think takes more Skill, Acyllic on the other hand is hard beacause u gotta wait for it all to dry before carrying on.