Tim Sweeney, founder of Epic Games, said NVIDIA's GeForce 7800 GTX (codenamed G70) will be faster than ATI's upcoming R520 graphics core. During a video interview with NV News the interviewer asked Sweeney "R520 or G70?". Tim smiled and said, "Oh, G70 for sure."
But on the other hand you should bear in mind that Epic is participating in NVIDIA's "The way it is meant to be played" marketing program.
Some GeForce 7800 details can be found here and a few weeks ago we also posted an article about the heat production of the Geforce 7800. It is said that NVIDIA's GeForce 7800 won't get so hot as its predecessors.
The GeForce 7800 will likely be launched within two weeks at Computex (May 31 - June 4) in Taiwan.