The wife is letting me knock the dust off my wallet (Wish it was my zipper) and letting me buy a games machine. So the question is, what do i go with?

I have a buddy (yes, it's true) who wants me to go with the PS3 so we can play football against each other on-line, but I am still not sure. During the football game today a add said you can buy a x-box for 100 bucks cheaper than a PS3.

I have never bought a games machine before so any help would be great.