Tested Both
Well, today, I tested both of these extensively, and I must say...
I like the Parallels beta better.
Concurrency works very well if you auto hide the dock and put it on the bottom. that way, the Windows taskbar extends across the whole bottom.
VMWare was extremely slow for my Intel MBP C2D compared to Parallels. Both were clean copies of Windows. 3d is still crappy in both....but it's better in Parallels.
Obviously, here's what going to happen soon: everyone will simply make a BootCamp partition, and then parallels/vmware will simply be a program that allows you to run the partition inside mac os. Obviously Parallels has a head start on this, though alot of developers in my area say that it's very buggy in this beta. Like everything Parallels has done so far, it keeps getting better, and will continue to get better.
I will say this about VMWare: if you want to run Solaris, VMWare Fusion works alot better. Parallels is definitely focusing in on XP/Vista, whereas VMWare treats all os virtualizations equally.
Chad Z