my only experience with PS3 vs 360 is that my PS3 fanboy mate joins us on the 360 and the one time he joined us for a party ground war session, he left within 3 minutes complaining about lag, campers and shit players :lol
I think he was just annoyed cos he was losing to be honest. He didn't really try to adjust to the controller or whatever.
He's apparently a really good player on the PS3, he must be on his 4th/5th prestige by now and he's non prestige 14 on xbox and he was getting owned basically.
I have another PS3 fanboy friend who did manage to make the adjustment in order to play with us and he's very good on the 360, not sure if he was any better on the PS3 though.
bottom line is its individual how good or bad someone is at anything (obviously), and xbox live has more of both!
but if it was the same person, xbox controller allows them to be better at the game.