I find the controller on the xbox far more comfortable, in both short and long gaming sessions. The playstation controller feels like it'll fall apart in your hands.
the xbox has removable battery packs, you can buy rechargeable battery packs and have separate batteries charged. The PS3 has a built in battery that will die and you have to charge (or have plugged into a usb port) to play using the same controller.
Both have exclusive games, and both share some of the greatest titles out there right now. Both prices are about the same for games.
Accessories are where things shine... The XBox will have Project Natal released this winter, it's a motion sensitive bar which will allow you to literally be a part of games; it'll be a revolution in gaming. The PS3 will have some gay little wand that makes you look like harry potter and won't be able to compete with XBox's Natal.
The XBox has a webcam that you can use for live camera sessions (video conferencing basically), has "party mode" which allows you and friends to have up to a 16 person conversation outside of a game (which the ps3 doesn't).
