I'd say they are both pretty good, but I feel that the Xbox 360 is superior.
Why?
Well, I play a lot of online shooters(Call of Duty, mostly) and the way the controller is makes it extremely easy to play them, a lot more than the PS3. The triggers and bumpers are great, but the thumbsticks could be different. There are a lot of people that prefer the PS3 thumbsticks.
Xbox 360 also gets most of the downloadable content for online games before the PC and PS3, so I'm also happy there, because then I get to play it sooner, and I love my online shooters. The sooner I get the map packs the better. I just love owning those 12 year-old XBL noobs that cuss at you when they lose because I use a super awesome headset.
Speaking of the headset, Xbox 360 has better ones. Better ones made by other companies, that is. Turtle Beach makes outstanding headsets, but only have a few for the PS3, and none of those are wireless and have worse performance than those that the Xbox 360 has. I have wireless TB X41s for my 360 and they are AMAZING. Only for Xbox 360, too.
The Xbox 360 has really no hardware problems anymore, either. They integrated the graphics into the processor to prevent red ringing due to graphical errors(which a majority of the red rings are from) and also added another fan on top of the console to help prevent overheating, and even a way to completely prevent overheating. When it beings to overheat, the console warns you that it is going to shut itself off to prevent overheating, and a red dot will appear on the power button, and it will only turn back on after that red dot it gone. So, I'm trusting this Xbox 360 to not fail on me.
The PS3 does have some perks, like Bluray, but I don't care much about that, and none of the other advantages are anything to me, really. The only reason I would get a PS3 is for the exclusives like Heavy Rain, GoW3, etc. I am very content with my Xbox 360 and its perks.