The PS3 and the XBOX360 share most of the third party library. I am not really interested in shooter and I don't like to pay a fee for going online.
I don't see why I should buy both consoles. The only games that I am missing out are Tales of Vesperia and The Last Remnant. The PS3 offered me Metal Gear Solid 4, Ratchet and Clank, Uncharted, God of War and a good backlog of PS2 Games/HD-Remakes.
The advantage of the PS3 is that Sony has the support of both western and japanese developers.