BF3 at 2,560x1,600
The 2,560x1,600 FXAA numbers are very similar to the 1080p 4x MSAA's. Sapphire's card does well again and the game is just about playable on the Ultra setting.
But 4x MSAA continues to trip the Radeon HD 6970 up a touch, comparatively speaking. We'd not feel comfortable playing at this setting on any of these high-end cards meaning a dual-GPU solution is called for here.
Battlefield 3 summary
Evaluated on a price-to-price basis and looking at the Battlefield 3 scores, NVIDIA and AMD's high-end single-GPU cards are roughly level pegging, though NVIDIA pulls out the slightest of leads if you choose to use MSAA.
What we can say is that you'll need a beefy GPU to play the game at the highest image-quality settings.
