Out of the two, I'd pick the 360 anyday of the week. Me and my younger brother picked up the 360 and the PS3 as our birthday presents in April, and since it's been lying around in the house, I can easily say he's played on my 360 more than his own PS3. There just aren't the same good games out, Motorstorm looked good but is in fact more annoying than anything, the first two times you hit a wall you think 'wow how pretty', but after that, nobody cares.
The thing i liked about the ps3 is the constant updates, its as if Sony actually give a damn to what the community want, rather than MS who pick a feature at random and then choose to implement it. For something being touted as a Media Center Extender, it sure as hell doesn't do much good. Without MCE installed on your computer, it's useless, everything needs converting to WMV.
Although everyone with a PS3 will say how its great to not have to pay a monthly sub to use online facilities, I think the cost of Xbox Live is well justified. PSN has a handful (if that) of titles available on it, Live has demos of every major game, and a whole load of extra media types (movies et all in the US), it also has an awesome Live Arcade.
It's a hard choice, I like the PS3 a lot, but the lack of a decent online experience, lack of vibration in the controllers, and a poor game lineup at the moment means at this moment in time, I'd have the 360 over the PS3.