Performance in Semi-Synthetic Benchmarks
Multi-GPU solutions from ATI and NVIDIA act almost identically here in pure mode (that is with disabled FSAA). The systems with two RADEON X850 XT and two GeForce 6800 Ultra run almost neck and neck and demonstrate similar performance improvement compared with a single-card mode. With enabled FSAA CrossFire takes the leading position in higher resolutions. However, if we compare the performance improvement in this mode, then NVIDIA SLI will look more efficient than the multi-GPU technology from ATI.
Final Fantasy XI Official Benchmark 3
You cannot benefit noticeably from CrossFire support in this game, so the laurels remain by GeForce 7800 GTX. However, to be fair, I should say that SLI technology is also of no particular use here.