The main argument I have against just phone + bluetooth is that you have to unlock your screen, keep it on, and it's a smaller size. I have wireless android auto set up, along with a magsafe case+charger, so my routine is to get in the car, slap the phone on the charger, and everything just comes up on my head unit display. For me it is way more convenient than having to deal with my phone display, and the larger screen is also better for navigation.
I have yet to hear any real negative points against AA or CarPlay for that matter, mostly it comes down to preferences like yours rather than actual interface issues.
If you're talking an Android tablet/headunit, separate from Android Auto, that makes sense... But Android Auto is essentially a simplified interface for specific apps installed on your phone, and is generally quicker and safer than using the phone interface. No one here is arguing for a separate android console interface, so I'm not sure we're talking about the same things. The whole point of Android Auto is to take a separate interface and OS out of the equation and to allow you to use your phone as the brain.