Our team is currently running a blog series to demystify some of the misinformation, rumors, etc that exist in the market today concerning ESX versus Hyper-V. Chris Avis posted today's article in the series which centers around patching, security, and functionality. One thing I would add is, even if you purchase ESX licensing, without vCenter you are still sunk when it comes to moving the virtual machines around. Heck who knows they might have to address this in a few weeks at VMWorld. Any takers? Alas..I digress... give the article a read here: http://blogs.technet.com/b/chrisavis/archive/2013/08/14/vmware-or-microsoft-simplified-microsoft-hyper-v-server-2012-host-patching-greater-security-and-more-uptime.aspx

You can find a complete list of the series here as well:

http://blogs.technet.com/b/kevinremde/archive/2013/08/12/vmware-or-microsoft-the-complete-series.aspx