I manage a server for the organization I work for, and CPanel X is the version used. It hosted on Kupio.
Yesterday I transfered my own personal server to Lunarpages, and CPanel 6 is the version used. It is hosted on Capricorn.
In both cases I did not request anything and these are as far as I know the default versions.
Why the difference? I'd rather have the same version (X) for both.