Quoting from SearchServerVirtualization:
..”Between Microsoft Virtual Server and [VMware] ESX, there’s no comparison,” said Chris Wolf, an independent consultant and author of Virtualization: From the Desktop to the Enterprise. “Bells and whistles-wise, ESX is still miles ahead of Virtual Server,” he said.
Over the course of his presentation, Wolf listed several areas where Microsoft has to work to bring Virtual Server up to snuff. For example, whereas VMware supports full access to the storage area network (SAN) within each virtual machine (VM), Microsoft Virtual Server guests access the SAN through a mount point or drive letter on the host operating system. Accessing the SAN this way adds latency, Wolf claims.
Wolf also called out the latency of the two platforms’ virtual disk implementations – the .vmdk file for VMware, and .vhd for Microsoft Virtual Server. VMware published tests that showed ESX Server latency at 13% when running with virtual (rather than physical) disks. Tests performed by the Australian consulting firm Capitalhead benchmarked Microsoft Virtual Server virtual hard drive latency at 28%…
Read the whole article at source.
While the comparison could be interesting Chris Wolf is comparing Microsoft Virtual Server with VMware ESX Server: I said so many times this is not possible.
Architecture (bare metal approach and optimized file system on ESX Server, just to name a couple) and prices are 2 points big enough to prevent any comparison from any point of view.