Depends on your personal taste.
The Playstation 3 is by far the better built of the two (Though I'm unsure about the redesigned PS3). Worth noting that recent 360's seem to be built much better and are close to being the reliable machine we always wished it was.
The Xbox 360 has the better controller, although it's sadly flawed due to having a horrible d-pad.
The Playstation 3 has much better multimedia capabilities out of the box, it's an excellent upscaling DVD player, plays Blu-Rays, has a internet browser, and other good multimedia options for such things as video files and mp3's.
The Xbox 360 has a superior online network that offers good online play, quick downloads, and excellent features like it's video store that put the PS3's one to shame the last time I tried it.
The PS3's online is free, and significant features seem to get added to it's firmware more often than the 360 gets anything. 360 seems to concentrate on refining what it already offers.
The integration of things like achievements, friend's list, etc., on the 360 is far better than the PS3.
Excellent to decent PSOne backwards compatibility depending on the title, and some models play PS2 games quite well, especially early US models with full hardware compatibility. Few BC Xbox titles run close to flawless on the 360.
Games tend to perform better on the 360, often being the lead development platform while the PS3 port of a specific title sometimes runs much poorer than on the 360, despite having a hardware advantage. Seems like the gap is closing or closed though as the PS3 grows its userbase forcing developers to pay more attention to their PS3 releases.
PS3 can take advantage of PC controllers in certain situations, such as USB flightsticks and throttles in at least 1 flight simulation and various Logitech and Fanatec wheel/pedal sets for racing sims. The 360 is limited to licensed 360 controllers.
The Xbox 360 is a year older than the PS3 and has a lot of nice bargain games from that era that are cheap to buy now, such as Call of Duty 2. That extra year on the market also means there's a larger variety of games available on the 360, though whatever advantage that provides is erased more everyweek as both platforms recieve most non 1st party releases these days.
The PS3's hardware is easily upgradeable with standard laptop harddrives. Expect to pay a very inflated premium to ever upgrade your 360 to a larger hard drive.
XBLA has a far more engaging selection of new titles than PSN does (Though there's still lots of nice PSN releases). However, the PSN's selection of older back catalog titles from the PSOne is getting better by the week while the Xbox Originals line is dead almost before it ever started. Both seem comparable with current generation game downloads (An area I've ignored, would rather buy a specific game on disc than pay the same amount to download it).
Netflix is something many 360 owners have enjoyed, but it will shortly be officially available on the PS3 as well. So they're comparable in that area.
That's pretty much how I view both consoles. They both have certain advantages and disadvantages. Personally, I enjoy the gaming experience of the 360 more, while I love the multimedia capabilities of the PS3. The PS3 also provides for the occasional excellent PS3 exclusive (Even in the download arena, GTI Club+, SumoDigital's remake of a classic Konami arcade racer, is excellent and not available on XBLA for one example). Also, despite preferring to game on the 360, I love that the occasional PS3 title, like IL-2 Sturmovik: Birds of Prey, allows me to use PC controllers to enjoy it unlike on the Xbox 360. Glad I have both, but strictly from a gaming perspective, the 360 has a definite edge.
Edited by Atariboy, Sun Oct 25, 2009 11:51 PM.