I wouldn't be surprised if Safari works really fast on OSX, FireFox works really fast on Linux, and Internet Explorer works fast on Windows.
Are these benchmarks tested on every OS available to see if they all work the same way? Hm....
You know, I wonder about this as well. I do find that the browser that comes with the OS seems to work better in the long run. Safari on my mac is for me pretty fast. On my PC desktop Internet Explorer while not the fastest, *works* better (as far as stability and website loading) than FF3, Chrome, and Safari.