Phoronix has recently begun a series of benchmark tests comparing Windows 7, Ubuntu 10.04, and, when possible, Mac OS X 10.6.3.
Platform allowing a side-by-side comparison of all three:
Processor: Intel Core 2 Duo CPU P7350 @ 2.00GHz (Total Cores: 2), Motherboard: Apple Mac-F22C86C8, Chipset: nVidia MCP79, Memory: 1 x 1 GB DDR3-1067MHz, Disk: 120GB FUJITSU MHZ2120B, Graphics: nVidia C79
512MB (450MHz), Audio: Realtek ALC889A, Monitor: DELL S2409W
Using this test platform, they came to the following, general conclusions regarding graphics/gaming performance involving OpenGL:
With every OpenGL gaming test and at every tested resolution, Microsoft Windows 7 x64 was significantly faster than Mac OS X 10.6.3 on Apple's very own hardware. In many cases, Windows 7 produced noticeably higher frame-rates than even Ubuntu 10.04 LTS "Lucid Lynx", which was somewhat surprising considering the competitive performance last week in our Windows vs. Ubuntu Linux performance comparison.
http://www.phoronix.com/scan.php?page=article&item=linux_windows_part3&num=1
I'm a little bit shocked at this. I would not have expected Windows to out-perform Mac on Apple's own hardware.
What's interesting for those of us who use Linux is that Ubuntu 10.04 is comparable to Windows and will likely run the Steam engine well.