Why in the fugging hell would anyone pay for Xbox LIVE? When you can pay $300 dollars for a Playstation3 and never get a bill for online play. All you need is to get wireless internet and you can play.
Quality is better on 360.
And don't stuffpost. I have MW2 for both systems (failed LAN attempt and lol outdated), and the xbox 360 connections were phenominally better. (Both are plugged in by ethernet cable. so no wireless. :P)
EDIT: You can buy a Xbox 360 and Xbox LIVE for $270 total.
DURP DURP