I've got both systems and thusfar, I like the PS3 better. For me it's more convienant and doesn't only play games -- Playing online is free, PS3 has a built in browser and it has no loading times compared to 360.
The only thing I like about the 360 besides Mass Effect is Sports games. I played Madden about half an hour on my friends PS3 [before I got mine] and then bought mine for 360 and it was hella smoother and looked better. I told myself that the 360 would be a sports game console with the addition of the 360 exclusives and the PS3 would be action games and of course its exclusives but ima see how Madden, NCAA Football and NBA2K looks and feels on the PS3 this year.
I say go with what you're more comfortable with. If you like FPS, go with the 360, but if you like everything else -- Metal Gear Solid and God of War, then PS3 is for you.