I've always liked Quentin more, probably just because it's the one I'm used to. But I prefer Quinn as a name on its own. You'd think I'd like Quintin, Quinten or Quinton with Quin(n) as a nn, but I don't at all. I don't mind Quincy or Quinlan, though. :b
They both look weird to me. My cat's name is Quinton, so I guess I am just used to that. We named him that because he was our fifth cat and he is fat and weighs a ton..haha, get it?? :PBut for a kid, I suppose I would go with Quintin.