It's a catch22. From my experience with Vista RC2, 64-bit runs much better than 32-bit (agree with Dee-27 on the speed), but then you need "signed" 64-bit drivers for all your hardware. And although 32-bit software will run in 64-bit Windows, you're not getting any additional advantage there.
I stopped using 64-bit Vista end of last year because there was no driver for my Matrox video-card and no SATA-RAID drivers for my mobo either. The disappointment was ever bigger with 32-bit when I couldn't burn DVD's properly on my nForce3 system. Look at the following "Create Disc" images and the Buffer and CPU Usage graphs.
First screenshot is 32-bit Vista, buffer and CPU go all funky in the second half of the burn. And this is only an RW-disc at 6X speed, 16X speed burning is out of the question. Second image is 64-bit Vista, rock steady buffer and low CPU usage all the way (CPU spikes at the beginning are just Vista doing its thing, file indexing or defender scanning, who knows - there was a lot of hard disk activity). Both are spanking clean installs on the same system as found in my sig, which I did this afternoon - to check that everything I've been saying here previously wasn't a fluke . Changing from (Vista provided) nVidia IDE drivers to standard IDE drivers on 32-bit didn't improve the issue.