Virtual machine shootout: Virtual PC vs. VMware
 

If you're interested in running applications, Virtual PC 2004 and VMware Workstation 4.5 are both competitive tools for the job. In fact, they're both so refined that your ultimate purchase decision will be affected more by your own needs than by any inherent problems with the programs. While general performance is an important consideration (and easily quantified), your eventual uses for the software are more important.

http://arstechnica.com/reviews/004/s...ines/vm-1.html