NVidias have been better optimized for OpenGL due to iD software beeing the writer of NV graphical benchmarks ... aka Doom3 ;-))
Not quite true. nVidia have always been producing top-of-the-line OpenGL ONLY cards for high end rendering purposes, so their GL support has always been quite good. It was ATI that -HAD- to quickly release a beta set of drivers that made OpenGL viable. Before then... I don't know what they were doing, but it seems like it was more of a nightmare than Doom3 itself...