you forgot Data Protection Manager
https://social.technet.microsoft.com/Forums/en-US/6e8bbabc-089f-42f1-8af1-8715df4a33a8/problem-with-dpm-2012-r2-console-after-install-ru5?forum=dataprotectionmanager
All repeat: 'never patch on a patchday'
Redmond's patchwork mess has extended to Virtual Machine manager, after a recent patch spoiled when exposed to the sun. Update Rollup 5 for Microsoft System Center 2012 R2 Virtual Machine Manager emerged in early February, promising security, reliability and networking improvements, plus support for SUSE Linux Enterprise …
"An order of magnitude fewer holes in Hyper-V Server than say ESX or KVM though."
Who cares when it's not open to the world and easier to patch in the first place? And those other two options don't discriminate on the platform I'm using to manage them from which is another big plus.