They trade blows here and there. The GTX+ is usually faster without AA, while the 4850 is generally faster with 8x AA. But it all depends on the game, resolution, settings... Not possible to make an absolute statement.

The OP should just read a few reviews and decide based on the results @ his monitor res, AA preference and games.

We are not helping him with so much subjectivity, 3dmark etc... there is plenty of concrete, solid evidence out there, so he can make an informed decision.