the ps3 has wireless built in, and the xbox you have to buy a wireless dongle.
not with the Xbox Slim you dont, wireless built in..
my tuppence worth, I am a gaming freak and own all 3 of the current machines...TWICE
Xbox wins for me, yes you have to pay £30 a year for Xbox Live but lets face it PS3 fanbois would fork out that eaisily if it meant they got a stable Black Ops online experience, which is massively flawed on PS3..
but what to suggest to someone buying one or t'other, look at the games/media capabilities..PS3 will have the edge as a media streamer and of course blu-ray, and Vidzone is a decent service and you have a web browser.... Xbox has a great film rental service that is currently ahead of PS3 and dedicated LastFM, Twitter, FB apps, media streaming also works well..
gamewise you have choices like, Gears of War or Resistance, Forza or GT5, and online wise gaming is and for a long time will be smoother/easier on Xbox.
non standard controller gaming, as I say I have all 3 twice and without a doubt Kinect is the most awesome, its so responsive and you can walk into the room where someone is playing and seconds later be in the game with them, its streets ahead tech wise... PS Move seems more responsive than Wii but it just comes across as a fake Wiimote.. one thing that I dont get with Kinect albeit is very impressive is non gaming control of the Xbox, I just prefer to use a controller to play/pause films and navigate the Xbox.
if you go for a Xbox DO NOT be tempted by a cheaper older model, go for the Slim, they have wireless built in and more stable hardware.
oh and a simple answer for me choosing Xbox over PS3, is a simple download game called Trials HD, seriously I have been a gaming addict for 30 yrs now and Trials HD will probably be top5 best games of all time, its just so addictive.