Unless you specifically need to run Vista I would suggest going with XP. XP seems to run much better and uses less resources than Vista under virtualization. You also have to factor in the hit to battery life that Vista seems to impose on all systems.

I own copies of both Parallels and Fusion and Fusion is much snappier and feels a bit more polished. I’m running XP along with Office 2007 with no issues.

Personally this was a no brainer… VMware all the way.

I’ve been using a Mac at home for about three years now and I’ve finally brought an Intel Mac into the family (so that’s me running G4, G5 and Core2Duo :) ) however, my day job is purely Windows based. Using Fusion, I can work on a VM at home on my Mac, transfer it to a USB stick, carry it into a clients office and using their Windows based hardware, keep on working on it using the free VMware Player / Server or even commercial versions like Workstation / ESX etc etc… to me, that is a killer feature.

Also, as other virtualisation products tend to compete with VMware, it’s more likely I’ll find tools to convert my Fusion images to other formats, should the time come that Fusion fails to meet my needs.