Hypervisor type is the important factor on this point.
If you are using Vmware on Windows system , it is type 2 and low performance but it is flexible. Type 2 (Vmware workstation, Virtual Oracle Box)
On the other hand, if you are using the system on the web (Vps, Vds) for Unix/Linux, it must be type 1 for higher performance also you can reinstall system without any support ( like ticket)
Type 1 ( Favourite KVM, Vmware Sphere)