For sure if you kill Apple Maps it will revert back to BMW Nav. But sometimes, just stopping navigation on Apple Maps will restore BMW Nav.
I do like BMW maps for the following reasons:
1) AR view is nice. Arrows are helpful when driving in an unfamiliar area
2) Automatic lane changes only work with BMW Nav. Not critical, but it's pretty cool when it works.
3) Pre-condition the battery before arriving at DCFC stations
I use BMW Nav for about 15% of the time, otherwise, for 80% of cases, I use Apple Maps. It's too convenient to just click on an address in Yelp and have Apple Maps start routing when I get to my car.
Then for the remaining 5% of cases, when I'm running late and absolutely, positively must avoid traffic, I use Waze. In the the recent months I've found Apple Maps to be very close Waze when I've compared the routing.
Ironically since I've purchased my iX three months ago, I enjoy using the DAPP to drive me, and just kicking back and listening to music and podcasts in the comfortable seats. The 5 minutes that Waze saves me isn't work 5 minute less enjoying the wonderful iX!