Internal Virtualization

[john_sm3853]

I am new to virtualization and I am working on putting an Internal Virtualization plan in place. I will greatly appreciate if you could help me understand, Under what circumstances is VMWare Virtualization and/or RHEV and/or Xen and/or Microsoft Hyper V is better over the rest. Also, is it reasonable to assume, all that needed to be virtualized on VMware has already occured. Thanks for your help