System Center Virtual Machine Manager (SCVMM) manages multiple vendors' hypervisors. Easily.

VCenter's Multiple Hypervisor Manager "can only SUGGEST workarounds or configuration changes, but actual issue resolution must be handled by the third-party hypervisor vendor."

So in a nutshell: VCenter is basically read-only management with no configuration ability... while SCVMM is COMPLETE management and operation of your virtualization environment.