(1)Severus Snape
(1)Albus Percival Wulfric Brian Dumbledore
...Damn, this should probably be the final; semis are still cool I guess.
Screen time is irrelevant, they've both got more than enough.
Neither character is particularly relateable, and I have no inclination to dress up as either for halloween. So...that's not a factor for me this time around.
Depth...they're a clear case for #1 and #2 in the series as far as character development, and surprises about the characters.
Style...Snape's got plenty--see the part where he talks circles around Bellatrix, or completely shuts down Harry in 1v1, or has an awesome duel with McGonigal. I think Dumbledore's probably going to win style if I go into a quotefest, but not to the point that I think it should decide the match, except maybe as a tiebreaker.
Humor--Dumbledore's got it, Snape doesn't.
So...it really comes down to: Dumbledore's ahead in a couple of flashy silly categories, and they're both quite good at character depth. Is Snape better at character depth, and not only that but better by a large-enough margin that I'd vote for him over Dumbledore? And...I mean, I think there is some argument here--it bugs me that Dumbledore's characterization was not foreshadowed, unlike Snape who had amazing foreshadowing, and even when we get Dumbledore's past revealed, Rowling didn't tell us some details like that he was gay until after the book.
Umm...hmm...let me think about this. No vote for now.
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Cats land on their feet. Toast lands peanut butter side down. A cat with toast strapped to its back will hover above the ground in a state of quantum indecision