Ok...I have to do this. I've spent a lot of time with XP Pro 32 and 64, and Vista Ultimate 32 and 64. For now I say stick with XP 32. As a gamer, we're taught that we're supposed to be on the curve, get the newest and greatest stuff out there. That works with everything EXCEPT operating systems.
First my rant on Vista:
Microsoft isn't fully backing their new workhorse, Vista, which is a bad sign for users. They've extended support for XP (realize that this is jawdropping news in the computer world) and are already in the Alpha stages of their next OS release, Microsoft Seven (2010). It's normal for Microsoft to start it's next OS soon after the public release of it's current model, but work on "Seven" has already been underway for over a year...scary. Even the developers of Vista put up videos on youtube, which of course were deleted soon after, complaining about how it clumsily worked. If you're worried about DirectX 10 over 9.0c, don't. There is a lot of motion to crack 10 so it effectively works on XP. I've used Vista, and some of it's new features are really neat and good to have, but the fact that it will absolutely drain your hardware is a terrible, terrible thing. We're gamers. We crave speed and efficiency. Vista is not efficient, XP is kinda. XP 32 is hindered by the 3.333Gigs of RAM cap, but it's worth it because the system itself doesn't need nearly as much to get off the ground.
32 or 64?:
The idea of 64-bit processors is a great one. The potential there is incredible compared to 32. The unfortunate thing is that companies have been hesitant to move to 64-bit because we live in a 32-bit world. It really sucks. I'd love to have a 64-bit OS with some amazing capabilities but that's just not happening. If you're looking to play games, most issues can be resolved with updating drivers and tweaking the system, but the benefits really don't outweigh the bad notes.
What it really comes down to is "computing friction." With more processes running at once, you're computer will be slowed down dramatically. Vista has A LOT of processes that it runs in the background, and if you try to shut them down your system will become unstable. I'm an IT and IS major, Microsoft is my life in a manner of speaking. I have to say, without a doubt, stick with XP 32 and hope that Microsoft Seven works better.
Edit: You're right Lafinass, crack is the wrong word. There are people still working, or at least pressing, on 9.0c to raise its capabilities. Sry =).