Once MC sees CCA as a DLNA device you can change the output zone in Gizmo to the CCA instead of casting directly from Gizmo. It's more versatile, and the CCA can play 96/24 source material, whereas I believe everything gets transcoded to mp3 when you play through Gizmo. I could be wrong about that, as I seldom play through Gizmo anymore.
If you're casting from Gizmo your phone needs to have a good WiFi connection all the time. If you use Gizmo to play to the CCA via DLNA you can walk out of the WiFi zone (say, into the garage to throw out the garbage) and the music will continue to play through the CCA system.