I've never read Scott Pilgrim and haven't had a chance to see the movie yet. I am a huge Mark Millar fan and loved both the Kick-Ass comic and movie. By default I vote for Kick-Ass.
Scott Pilgrim's at a disadvantage off the block as no one's actually seen it
They're very different movies though, different action, different humour. I enjoyed Kick-Ass, it was fun, but Scott Pilgrim did things I haven't seen in movies before, every Evil-Ex battle was a completely different kind of awesome. I think it was MORE fun.
As far as comics are concerned though I think both movies improved upon their respective source material, something you can't usually say.
Haven't seen Scott Pilgrim yet, but I'm 100% sure Kick Ass would win for me, because I adore it so much. There aren't many movies out there I would choose over it.
while Kick Ass was a really good movie, for me personally Scott Pilgrim is much more satisfying. I've seen this movie twice - i never go to the movies twice to see the same movie. i could go see it again.