It depends on the level. The first one is really great for HUNK.
Ada & Wesker are really great on the castle. Same for the waterworld level. Krauser pretty much owns on all. Especially on the Wii, as aiming is so much more accurate, for his bow.
Oh, and as for Leon, he's harder to play with, in comparision to the others, his weapon set seems less effective, against any given boss.