One key reasons for not buying the BS5 (yet) is that I have no idea where I'd hide the BM5. The BC2 'socket box' was bad enough and, as my large kitchen/living room is painted white, there's a fairly large black socket box on the wall. Looks a tad odd.
However, the BM5 is a lot larger. So, where do you hide this box? I don't want to buy a cabinet, it can't really go on the wall, nor on the floor. Got no problems with the BS5 size or design.
I wonder why B&O couldn't get the BM5 smaller, when Apple can get the Apple TV or the five-year-old Mac Mini far smaller? Makes disguising or hiding it, tricky.