Updated from xp64 to win7 on my driving cab pc. Same emulators, same settings, the games ran the same.
Some like California Speed were just barely maintaining 100%, so I'd be able to tell if there were much difference. (calspeed is the same hardware as nfl blitz)
This wasn't an issue on my driving cab, but when I updated to the latest NVidia driver on my stand-up cab the performance went to crap.
NFL Blitz went from running full speed to being unplayable. Reverted to an older one and everything was back to full speed.