No, its not. Windows drivers are generally faster. The reason behind it is simple: games. GPU vendors can sell more cards if they are performing better in games, this is why they optimise the heck out of the drivers to make common API usage scenarios faster. Modern GPU drivers are a huge mess, as they contain lots of hacks which would allow them to perform better in games, up to on-the-fly shader rewriting and other stuff. The reason DirectX is slightly faster then GL on Windows, is simply because more games use DX so vendors would concentrate on speeding that API up. In contrast, Apple's implementation is still fairly generic.
I do believe that we need a new kind of API... an API that would most closely expose the modern GPU hardware. OpenGL would still need a major clean-up, but the core profiles are a big step up. I am still very disappointed that the original Longs Peak didn't fly, that was a very elegant API design...
