In my tests, the Virtual PC VMs performed well compared with running a physical system with the same OS. The main difference between running a VM and a physical system is that in the VM, the right-Alt+Del key combination replaces the Ctrl+Alt+Del key combination. With VM Additions installed, Virtual PC supports high-resolution SVGA displays and provides full SoundBlaster and CD-ROM access. However, Virtual PC doesn't support USB devices.
Moving Virtual PC VMs between hosts is easy. Virtual PC stores its virtual hard disk images in a .vhd file and its virtual machine configuration as XML in a .vms file. To move the VM, you simply copy these files to the new host and select the existing VM through the Virtual PC Console. Virtual PC lets you easily move and share virtual disks between VMs. In addition, Virtual PC's differencing disks let multiple users and multiple VMs use the same virtual hard disk. Virtual PC stores each user's changes in separate differencing files, letting multiple users share a base virtual disk and keep their own unique changes. VMware Workstation has a similar capability, but you must manually edit the virtual disk configuration files to enable it. Virtual PC doesn't support SCSI configurations; thus, you can't use it for setting up Windows clusters.
An important technical advantage of Virtual PC is its ability to address up to 4GB of RAM, which gives it significantly more headroom to run multiple VMs simultaneously. VMware Workstation is limited to 1GB of RAM for all VMs.
Virtual PC came with a thin 28-page Getting Started guide that wasn't helpful to me. I found the product's task-based help decidedly inferior to the much more detailed help offered in VMware Workstation. However, Microsoft provides additional information about Virtual PC at http://www.microsoft.com/virtualpc. Virtual PC comes with standard Microsoft support. You can also obtain answers to technical questions about Virtual PC from the Microsoft Virtual PC public newsgroup at microsoft.public.virtualpc.
Making a Choice
I found VMware Workstation and Virtual PC to be of excellent quality. I had no real problems with either product. VMware Workstation is the more flexible of the two offerings. VMware officially supports a wider range of host and guest OSs than Virtual PC does. VMware Workstation has more advanced network functionality than Virtual PC does and unofficially supports virtual SCSI for setting up test clusters. Virtual PC doesn't support virtual SCSI and doesn't officially support the Windows server OSs required for setting up a cluster. If you want to set up test clusters, run Linux distributions, or run Windows server products, VMware Workstation is the clear choice.
Virtual PC is the better value of the two products. Priced $60 less than VMware Workstation, Virtual PC offers most of the same capabilities for Windows desktop OSs as VMware Workstation. Although Virtual PC doesn't support Linux hosts, it lets you run most x86 OSs as guests. In addition, Virtual PC's ability to address more RAM lets it run more VMs at the same time. If you want to run only Windows desktop hosts or primarily Windows guests, Virtual PC is the better choice.