We’ve been using Thief 3 in our graphics card reviews for a while now and it has always proven to be very demanding. This continues to be the case with both cards not being particularly playable at higher settings. If you’re buying the 6800 you’ll be looking at 1600x1200 No AA/AF as the best setting for the Radeon it would be 1280x960 with 4xAA 8xAF. So the decision on this game comes down to whether higher res or AA/AF is more important to you.