You know, they say there are no dumb questions, but this one...
Neither game is out yet. Best you can do is
recent benches of the leaked HL2 alpha at digit-life. The 6800s actually perform quite well; the 5950U still loses to the 9600Pro.
Edit: interestingly, the benches seem to have changed in the last month. The ATI cards all lost a few percent, and the NVIDIA cards gained noticeably. The 5900U is now about as fast as a 9600XT, and the 5950U actually beats the 9800NP. However, these results are still from a very early version of the game, and the final game may differ significantly in terms of performance.