System requirement for VUU is same as vSphere client.VUU complies the list of esx/esxi host using vSphere client which you used to directly connect to ESX/ESXi.
You cannot migrate VM from one datacenter to another datacenter but on other hand you can clone vm to another datacenter.
When you add esxi host to vCenter you get additional option to enable lockdown mode. If you enable lockdown mode no one can directly log into to esxi host using vSphere client. This option is not available for ESX.