As you can see, the 570 is about the same as the 480, with maybe the gtx 570 being a touch faster. The 570 will use less power than the 480, so I would go with the 570 unless you can grab the 480 for a decent amount less.
No experience with the 480, but I have an EVGA 570gtx sc and it rocks solid. Playing BF3 on ultra with no hiccups on 1920x1080 with no probs. Not sure what kind of frames I'm getting, never tested it as I'm not too concerned as long as the game runs smooth.
Yea, I've noticed on FPS, it's back and forth between different games... I'm more worried about the fact that the 480 can get really hot. I've got good airflow in my case, but I'm not sure if the 480 can push out more air to keep cool by raising fan speeds.
I can find a 480 for about 80-100 bucks cheaper than the 570 which is the reason for this thread.