in contrast to europcar it is very rare that you get an external navigation system, usually they are integrated.
3series exist only with sat nav as far as I have seen.

I only had one rental once at stachus, kind of tricky to find the entrance for returning the car. but when I was there they didnt make it complicated. gave me a volvo xc70 for cxmr rental (with sixt plat)

in that area it is the biggest station in munic I think, therefore biggest choice of cars, so I would stick with it.