as I have stated in other posts.

32 vs 64 only reason not to go 64bit nowdays is if your Hardware is to old and cant support it.

Vista64 vs Windows 7 64 Very little actual performance difference at this time. Though windows 7 will handle SSD and some future hardware better.

However there is a Big Percived Performance increase for gamers, this has to do with how windows 7 handles Hardrive access and Video, windows 7 gives smoother access and smoother grafics for less stutter thus giving a greater Percived performance. in other words windows 7 gives more sustaned performance with less spikes thus inhancing our game experiance.