I personally suggest you run with FXAA as it seems to give a good 5fps advantage and I personally cant see any visual difference at all..
Yeah I noticed that too. Can't see the difference between all the AA settings so FXAA is the way to go to get some AA and don't hit the performance.
Another chap just suggested to me that SFAA gives the same FPS with better quality AA. Going to try it now and see.