Found this interesting article of testing the graphics card performance not only on raw FPS but the latency between frames which can show as stuttering.
TL;DR version would be something like:
Even if card A has higher average FPS than card B, card A might frequently have big lagspikes which makes the game look shit outside benchmarking and in real world use.
Apparently Radeon 7950 with latest few driver versions has suffered from this problem pretty badly, and makes me wonder about the generally accepted best value for money cards list.