Windows 7 has DX11, TRIMM, and faster performance all around as well.
To top it off I think they stopped support for Windows XP, so that means no more updates (I could be wrong, but I know SP3 was is their last big support).
XP sp3 will be supported by MS through april 2014....i believe. http://news.softpedia.com/news/Windows-XP-SP3-And-So-It-Ends-88491.shtml
sp2 support ended july 13 2010. As much as i believe that win xp is the best os microsoft made, I do have to bite the bullet and agree that win 7 is better for more than 90% of the games out, unless you are playing really old legacy games...say pre win xp, than xp is better for those.