Yeah, it's really an odd comparison since they're at completely different price points. That being said, the GTX 480 should be immediately taken off the table. If you read the GTX 560 Ti review on Guru3D they include the 480 and 570 in the charts for Modern Warfare 2, Far Cry 2, Crysis Warhead, Metro 2033, Dirt 2, Bad Company 2, and 3DMark 11. In these 7 benchmarks the GTX 570 averages a 2% INCREASE in performance over the GTX 480 while also being $30 CHEAPER on Newegg, AND consuming less power, AND producing less heat...kind of a no brainer.
Now, the 570 compared to the 560 in those same benchmarks offers a 17.6% increase in performance for a roughly $60 premium. All-in-all, it depends on how much performance your friend wants/needs and how he feels about mail-in-rebates...