My wife has Android Auto on her Bolt. I would describe the difference between the Tesla UI and the Android Auto UI the same way I described the difference between my Dish Network DVR circa 2010 and the standard crappy cable company DVR of the same era. I.e. the Android Auto interface seems ancient, slow, sluggish, clunky and problematic compared to Tesla's.
Okay, I will be fair. Some part's of Tesla's UI need a lot of work as well. The audio interface could use a lot of work, and until recently, text support was non-existent (although to be honest, I'm not getting many texts these days--other apps seem to be taking over).
Maybe the Bolt's implementation of Android Auto is really poor, but personally I am really glad that I can just hop into my car and have all the functionality of the Tesla UI available to me without having to plug my phone into the USB port.
So the advantages of an Android Auto (or Carplay) type solution would be a consistent and familiar interface for everyone, and perhaps higher quality and even third-party apps with even more frequent update cycles than even Tesla (this is a double edged sword, of course!) But from what I've seen, Android Auto is just too far behind the native Tesla apps to make it worth it for me now.