GeForce GTX 480 Reference Board
From VR-Zone, the GeForce GTX 470 is up to 10% faster than a Radeon HD 5850 and a GeForce GTX 480 is up to 10% faster than a Radeon HD 5870. But this small gain in performce comes with a mega-power consumption: the TDP of the GTX 480 is equivalent to the HD 5970 one (see the TDP database HERE)!!!
Hardware-Infos has also some benchmarks with a GTX 470 vs a HD 5870.
But as usual, don’t trust too much these benchmarks, take them with a grain of salt…