FPS whores will probably want Vista 32 ... there are only 2 games i tested that run faster in Vista 64 and they are FarCry and Hellgate: London ... and IF you play those 2 games a lot, you WILL want Vista 64 ... there is significant improvement over Vista 32 in every way.
IF you have 4+GB of RAM there are also some possible advantages. Huge advantages with 64-bit games but only "possible" minor advantages in "loading/saving", in memory-mismanaged games and also if you are an 'extreme multi-tasker'. None of my "stopwatch" tests were conclusive; since i have an average "cluttered" system with everything enabled [including ReadyBoost and System Restore] sometimes Vista 64 would be quicker and sometimes Vista 32. Even the Witcher showed no consistent differences....
So my own personal "D-day" has arrived ... it is Day 30 of my "trial" ... and MS is giving me the ULTIMATUM - activate or lose it ...
--that's easy, imo - for personal use - i'd rather have the very slight FPS increase and Vista32.
[i am done with FC and Hg:L]
But i DO see where some of you prefer the perceived slightly smoother experience in *some* memory mismanaged games and those who are also extreme maxi-multitasker; not needed for me.
As i UNINSTALL Vista 64, i have to say it is "THE FUTURE" . It is just as stable as Vista 32 and you have to 'nitpick' to find flaws as you trade the irritation of 'signed drivers' for slightly better security.
---So ... pick one ... don't feel bad picking either choice as it is not a "marriage". If you want you can be polygamous ... tri- or even quad-boot your OSes if it makes you feel especially "high end"
... so, if there is interest, i can format my results ... but one fact is pretty clear to me at least ... pick Vista ... forget XP