My honest answer both.

They both have their pluses.

PS3: free online, blu ray, less discs per longer game, usually has better graphics, usually cheaper over longer periods of time, exclusives usually score higher on average than 360, better overall tech specs, lower failure rate (than the older 360's).

Xbox: more of my friends have an Xbox so more playing with friends for me, online is much more stable, more exclusives, from what I've read more developers like developing for the 360, voice controls are much more superior, downloading games, patches, etc, is much more hassle free on the 360, more backwards compatibility than the PS3 (excluding the two models that offer it for ps2 games)