I didn't vote either of those poll options because they aren't the exact reasons I would put for one of them winning.
I say Dante is the rightful winner because he was doing the right thing, perhaps that has something to do with why he repeatedly sends Vergil packing in DMC3 and DMC1.
Though I like Vergil as much as anyone, I say that his quest to gain more power or whatever was perhaps a good end but his methods to get to that end were flawed. By that I mean he was willing to activate some evil tower out of the ground and unleash the gate to hell in order to get a bit of extra power.