The 360 is beyond any doubt an inferior piece of hardware. The 360 will overheat and break while the PS3 is only about 30 times more reliable, makes less noise and will last longer. It also plays bluray.
The main advantage for the 360 is that its cheaper. The other advantage was that it had more games, but the playing field is evening out for that now. 360 also has better online gaming if that is what you are into. Personally I dont do a lot of online gaming so I prefer the more reliable PS3.
The 360 does not require a bluray burner to play backups, which is nice and again cheaper. They also make you connect to x-box live to play games, which is a real pain in the ***.