Hernán Di Pietro usually write interesting articles about desktop virtualization products on his website.
Often you can also find benchmark tests and comparisons like in this case: Hernán reviewed VMware Workstation 4.5 and compared it with older 4.0 product. Then he also compared WS4.5 GuestOS performance when it runs Windows XP and when it runs Windows Server 2003.
Go on and read whole article here!