Well, there are major differences between PSN and XBOX Live.
PSN has better exclusives, in my opinion. It is also free, and with a good hardwire connection I never had a problem with it. However, PSN usually gets Downloadable Add-On Content later than Live, and PSN has been hacked before.
Live has inferior exclusives, in my opinion. It is also expensive. Live has never had a major security breech and gets Downloadable Add-On Content first.
I'll take PSN.