I think both systems are as good as each other and if it wasn't for the price I was have gotten a PS3, far more RPG's on that system also BLU-RAY!! I know there are RPG's on xBox aswell but not as many. There's mainly shooters.
However I will say this, while I don't game online(no proper internet connection, all I can afford is mobile broadband.) after the hacking on PSN I'll probably hold off for a fair bit yet.
Oh I rambled sorry :/ My answer is neither they are as good as each other!