Yes, Xbox, definitely. While you do have to pay for online play, you get what you pay for. Voice chat on every game, a party chat system where you can chat with several of your friends even if they're playing different games, and the achievement aspect is strangely addictive and makes you try to do things in your game that you would never do otherwise, giving you more game for your buck.
PS3 is a great Blu-ray player and will be upgradable to the 3D Blu-ray spec, but it just doesn't have the exclusive games that made the Genesis/SNES war so interesting.
My gamertag is doubleofive, if you want to hook up on Left 4 Dead 2, the only game I seem to be playing recently.