I had the X-Box 360 and gave it away and got a PS3.
PS3 gaming online is free, unlike Xbox
PS3 plays blu ray - good for movie and games alike
And the clincher, the 360 is sooo f***ing noisy. The fan is on all the time, and it can sounds like having the hoover on in the background, whereas PS3 is whisper quiet.
PS3 all day for me.
Also you have to keep the xbox power supply (which kicks out loads of heat) plugged in even when it's switched off otherwise it forgets the date and time.