Look at the console exclusives and see which ones you can't live without. In my experience, Xbox is mainly for first person shooter games, and PS3 has more variety going for it. Online play with PS3 is free, compared to paying for online play for Xbox. PS3 has a blue-ray player, and Xbox doesn't. That's just my personal impression though.

I went through the struggle of choosing too, and I went for the PS3.