Windows XP supports DirectX 9 Windows Vista supports DirectX 10 Windows 7 can do DirectX 11 Mac OS doesn't do DirectX at all. You can still play 2D puzzle games all day though. You probably don't want Linux.
All you have in higher editions, is essentially more programs that comes with Windows. That is all. These additional programs, is like any program on your computer, they do nothing until you start them. More software does not slow down your computer in anyway shape or form, unless you have programs that runs continuously on the back.. but that is a different story, as most don't (see system tray, or task manager for background programs running). Of course, reaching max capacity of your HDD is known to slow the computer down due to a lack of space of temp files, but that issue is no longer existent in today computers for most, with our ridiculously high capacity drives. So in result, Windows 7 Ultra Super Bare Bone edition and Windows 7 Super Ultra Ultimate edition, will provide 0 difference in your computer performance, and won't show, not even 1 fps change in your games. All you need for a great Windows 7 experience: - Dual core or more processor (~1.8GHz more or a less a few hundred MHz, based on your CPU model) - 4GB of RAM - Gaming GPU capable of running your games (obviously). Will your games run faster under Windows XP.. yes and no. If you have a Pentium 4, or something very old with <=2GB of RAM, and a old graphic card, then obviously a your game (assuming it's perfectly capable of running on the mentioned specification), will run slower, than if it was on Win7, as your current computer is unable to handle Windows 7. If you have a more modern computer, then you should not see any difference in real world results. (Benchmarks doesn't county, as OS optimization, including drivers optimizations plays a part, and a game that runs at 900fps down to 880fps is not something to worry about... If it runs at or above 60fps, it's all you need for an awesome gaming experience (you most likely have v-sync on in any case, to not get split image graphic when you move fast). @Rofl_Waffle, Vista supports DirectX11.. it's in Windows Update.
Just for the quote Mac and linux support open GL, and while few game use it, mac still have the opportunity to profit most valve game.
Id buy an Win 7 Home Premium x64 if i were you. Its not the worst, but not the best either. Its a medium version of Win 7. But it doesnt support multiple physically separate CPUs, just many cores/threads.
