Generally speaking, Windows XP will run the game better/faster than Windows 7. Some caveats with that.
XP needs more tending to as the background processes and registry tend to get pretty sloppy. That leads to many who will make the remark, "XP runs like a turd compared to 7." All that means is the person did a poor job maintaining his/her Windows XP system.
Sound performance will vary between XP and 7, depending on the sound device. Many sound card drivers, on XP, did some really atrocious things to the operating system. Those things cannot be done with 7 due to all the DRM it has.
XP and 7 have the same thread manager, so thread performance is identical between the two. This goes to multi-core CPU's. XP and 7 use the same exact thread manager. It still sucks, but it is all we have for Windows.
I prefer XP over 7, at the moment. For me, XP is easier to manage and keep clean than 7. 7 has a lot of things going on which you have no control over. It has some compatibility issues with some older programs as well. Then again, XP is not able to run some newer software intended for 7.
I also do a lot of video/audio editing and 7 is not very stable for this. The DRM manages to intrude in areas it has no business in, which creates some a number of issues. Most people will never run into these issues. I am one of the unfortunate that do. Most of it has to do with no clean way to implement ASIO drivers in 7, which are required by a number of high end audio editing packages.
