FXAA Performance
FXAA is clearly fast. On every video card we tested, FXAA 1 was faster in F.3.A.R. than traditional 2X MSAA, and 4X MSAA. With the GeForce GTX 580 at 2560x1600, FXAA was 13.3% faster than 2X AA and 52.8% faster than 4X AA. At 1920x1200, the GTX 570 was 24.8% faster with FXAA than 2X AA, and 51.6% faster with FXAA than 4X AA. With the GTX 560 Ti running F.3.A.R. at 1680x1050, FXAA was 23% faster than 2X AA and 50% faster than 4X AA.
The Radeon HD 6970 was 14.7% faster using FXAA at 2560x1600 than 2X AA, and 50.9% faster than 4X AA. At 1920x1200, FXAA performed about 16.1% faster than 2X AA with the HD 6950, and about 42% faster than 4X AA. Finally, the AMD Radeon HD 6870 gave us framerates that were on average approximately 15.8% faster with FXAA than with 2X AA, and 37.8% faster with FXAA than with 4X AA.
FXAA Image Quality
Compared to 2X AA, FXAA is uniformly superior. Compared to 4X AA, there are some I Q trade-offs, but the performance advantage that FXAA offers gives FXAA the advantage. In some areas, 4X AA offered slightly superior image quality, and in other areas FXAA is better.
Even though 4X AA offers slightly better hard edge aliasing reduction than FXAA, we still think FXAA is a better option in most circumstances. For starters, shader aliasing is reduced by FXAA but not MSAA. Alpha texture aliasing is reduced by FSAA, but not MSAA. Single-pixel aliasing is also reduced, as is sub-pixel aliasing. The flickering of very small objects or surfaces can be a big problem, and FXAA deals with it admirably while MSAA does not handle it at all.