I’ve been running them both for testing purposes without issue. But i’m on a quad core Mac Pro with 12GB of RAM. YMMV if you’re on an iMac or Macbook Pro. I will say to keep your VMs on a separate hard drive, preferably Firewire to avoid the CPU overhead of USB, or a second internal if you’re using a Mac Pro. It makes things run much faster in my experience.
If you’re running Aero in Win7 and you can’t afford to give it a lot of RAM, you may notice on occasion, but most of it gets accelerated by the GPU now, so it could be fine. XP obviously isn’t going to have a lot of the crap that Win7 included, so it will undoubtedly benchmark faster, but from a usage standpoint, if you’re doing development in VS2010, you should probably be in Win7.
In a VM, 32 vs 64 hasn’t made a difference for me thus far, I actually have to keep both around for testing, but I haven’t noticed a performance bump from x64. Unless you’re going to push enough RAM into it where you’d need x64 to take advantage of it, x32 should work fine and you likely wouldn’t notice the difference between the two. Once again, YMMV.
2Since my original post, I've upgraded to Sandybridge MBP 17" with 8gb of ram and the 2.3ghz i7 cpu and SSD. This machine runs VMWare + Win7 VERY well. I've allocated 4 cores (out of 8 virtual) cores and 4gb of ram to the VM, and it performs very very well. I started out using a dedicated hard drive partition, but now use a VMWare virtual partition. I feel like the whole machine performs better with the virtual partition. – Armen – 2011-05-27T01:36:57.510
Good stuff! Thank you for letting others know what you're running and how that is working out for you. – Paul – 2011-05-28T14:57:47.713
1One more bit of information -- I am using the Apple 500gb SSD. This is a FAST laptop; so perhaps i am configured suboptimally, but i can't really feel it given the horse power here. – Armen – 2011-06-06T00:13:51.147
@Paul: "a minimum of 4GB, preferably 6GB for the Virtual Machine" isn't accurate for 32bit Windows 7/XP - they can't see anything over 3.5GB – DeepSpace101 – 2012-08-09T22:46:51.233
@Sid - agreed, good catch. My mistake was to add "for the Virtual Machine," whereas it should say "for the host computer." I would add 6GB to the host, so it could allocate 4GB to the VM while keeping 2GB for itself. I'll edit to ensure that reflects correctly. – Paul – 2012-08-10T14:34:11.477