I have both.

The 360 is LOUD, more likely to have disc read failures, menu and layout is abit all over the place IMO, but the controller is very nice. Too bad it's not wireless.
EXPENSIVE to upgrade HDMI/HDD

The PS3 I use for everything. Watch DVD's, listen to music, play games.
It's quiet, pretty, very easy to use. Wireless controller works a charm.
Uses 2,5" HDD that is sensationally easy to upgrade, and it doesn't even breach your warranty.

In my mind the PS3 is superior in every way.

Only reason I still have the 360 is Forza 2.