FWIW - I have used all these systems in various cars Avin, Dynavin, Eonon and they all have various benefits.

For *this* particular car, much like my M5, I'm going to keep it stock. The current system is working great and I'm not going to press this car into daily driver duty so my preference is to leave it original. The BlueBus will work perfectly for music and phone calls.

If the screen or nav unit was bad, for sure I'd swap. I have the AVIN unit in my X5 3.0 which my wife and I drive regularly and I love it.