Last month Gartner released a paper titled:"How to Choose between Hyper-V and vSphere". The paper written by Thomas J. Bittman, is made available for free viewing by Microsoft, which actually tells something about the outcome of the paper already.
The paper covers acquisition costs, ease of management including operational complexity and cost and also covers functionality richness of both the VMware and Microsoft virtualization platform solutions.
Summary:
Microsoft has improved its server virtualization products to the point that IT leaders should assess their VMware investments and consider whether Microsoft makes sense. Compare acquisition costs, ease of management and functionality for the two vendors and take advantage of their competitiveness.