I have already cooked a common sole once before, and have skinned only the upper side (the dark side). The result was quite tasty. However, some people say that there's no need to skin it. For what recipes would you pan-dress a sole by skinning it, and for what recipes would you leave the skin on, and why?
I would say it's totally up to you.
I prefer it with the skin still on, it get's really juicy inside. However it's a bit more difficult to eat. So perhaps if you were making it for kids (although, you could just skin them after they are fried), you could skin it.
One opportunity I really think is better without skin is when you serve it with sauce. Having to fiddle around with the skin covered in sauce is not really handy nor fun.