I would say that Mythbuntu is the most straightforward way to get MythTV and a full desktop environment, as it already comes with the lightweight XFCE desktop environment.
Straight from the source:
Mythbuntu uses the XFCE desktop. All unnecessary standard Ubuntu applications such as LibreOffice, Evolution, and a full Gnome desktop are not installed in a default Mythbuntu install. If at any time a user wants to, they can install ubuntu-desktop, kubuntu-desktop, or xubuntu-desktop and add a full desktop onto their installation. This can easily be done via the Mythbuntu Control Centre.