Get the 360!!! I've owned a 360 for years now, never any problems (you gotta take good care of it) and spent immense hours playing Forza 2, Forza 3, COD titles, various RPGs. 360 is THE gaming console. I bought a PS3 this past December because most of my close friends play Black Ops on it, and because GT5 was coming out (granted I've been a bit disappointed, but hey whatever). If you are looking for online competition, legitimate competition, go for 360 for this reason. There are a ton more XBL users than PSN users and you get a much more competitive gaming experience. When Forza 3 was in its prime time release the online racing was great and quite difficult. GT5 online racing is just...bleh. And a further but unrelated example to this particular thread: On an average night you can find 600,000 people playing Black Ops on 360, while about 300,000-400,000 play the same game on PS3. I've kept close attention to these numbers since the middle of December, and though it's just for one game (even though it's the most played online game right now) it is fair to deduce that more people are playing 360 than PS3.
Really as a console the only thing I see the Playstation having over the 360 is Blu Ray support and the multitasking capability. In my opinion the line of 360 games contains more depth, variety, and overall innovation. Pair this with the great benefits of XBL, and a gamepad that doesn't suck...you've got yourself a great deal. Don't throw your PS3 in the closet (per se), but if you've got the money and are looking for a valuable gaming experience, join the 360 population.