[Legion]

With vista sp1 out there is no longer any reason not to use vista when it comes to gaming.

Vista sp1 solves the performance issues vista has had.

http://www.extremetech.com/article2/...2302495,00.asp

Final Thoughts

If you were expecting a huge drop in performance as your eyes scanned from the XP to the Vista results, well, surprise! As many a tech analyst predicted, Windows Vista's gaming performance conundrum has largely been solved, and it was mainly due to early graphics drivers. In fact, I'd been planning to run a few other gaming tests, but the results from these were so uninteresting that further work didn't seem merited. Love it or hate it, Vista is performing far better than it used to.
Game performance, it seems, has been exorcised from your concern when choosing a Microsoft operating system. That leaves a few other factors, of course: stability, responsiveness, eye candy, price, DirectX version, and a few other odds and ends.
It took about a year and a half, but the performance gap between Vista and its forerunner has finally evaporated.