there isn't any kind of information yet on which is better. If they are close to the same quality I would get it on the 360 for the same reasons that twestern said.
also, I like getting games on the 360 because even if it isn't multiplayer, I can see when my friends get on and maybe jump into a multiplayer game.
Thats one of the big reason's My game collection is so lopsided right now. I get all my multiplats ont the 360 not because I prefer it, but because all my friends prefer it. I have 74 people on my friends list on xbox live versus 8 on the playstation network.
People in America just like xbox a lot better I guess...