I've always been about the PC - better performance by far and you can upgrade them whenever you like - they're pretty much futureproof for a good five or six years as long as your rig has got the space for bigger graphics cards and more memory. The PC I'm typing this on was bought in '07 and it still plays all the latest games - I can't see me upgrading for another two years at least.
I haven't owned a console since the original Playstation back in 96 and I sold that to a mate so I could put the money towards my first PC.
To answer the original question though, if I had to choose, I would pick PS3 over XBox360, but I prefer the XBox 360 control pad.