When I used Windows x64, I never really ran into issues. If you have above 3 Gigs of ram in a 32 bit system you might actually run into Vista update problems so I would recommend just going with the 64 bit OS; however, with only 4 gigabytes of ram both operating systems will probably end up performing the same. <-- But from my experience, I ran into more problems having more than 3 gigs on 32 bit vista than with working with 64 bit vista.