I find the Android Auto screen to be decidedly low tech compared to Sync 3. Google and Waze maps are not any better than the factory nav as far as getting you to your destination. The Sirus Travel Link that comes with the factory nav is every bit as good as Google or Waze for letting you know about traffic, construction, accidents and POIs.
As far as updates go there are two new housing developments that folks started moving into 1.5 to 2 years ago and neither road shows up on Google Maps or Waze so the update advantage spoken of with these apps is very much over stated.
The biggest disadvantage to Android Auto is it has to be plugged in via USB, doesn't work over Bluetooth. For me that means I have to use the USB port that barely can keep up with my phone or the fast charger that will charge the phone in about an hour.