(1) Irrespective of the lenses used (Zeiss Otus for example), a Nikon 810 or Canon 5ds can't produce detail that the sensor can't pickup to begin with. A small sensor can't resolve the detail that a larger sensor can even if you put an average kit lens on a 300mp camera. You'll get more detail with the kit lens and larger sensor compared to a great lens on a smaller sensor.

(2) I can use a run-of-the-mill 55mm f/2.8 lens on the 645Z and get better detail than using an Otus lens on my Canon or Nikon. Who cares what's sharper out-of-camera? The fact of the matter is that once the files are processed and sharpened, the detail is ultimately better from the larger CMOS sensor practically every time. I wouldn't go gaga over using an Otus lens on a small sensor camera... it's like a microbiologist using expensive highest quality glass slides to put samples on, when s/he's using a $50 microscope. It doesn't make sense.

(3) Many aren't used to shooting medium format (MF) and still think that MF are horrible when raising the iso. This hasn't been true for years now. Every since MF started using CMOS sensors, MF has been the highest quality high iso shooters on the market, and it is still that way today. You cannot get the same high iso quality from a Canon, Nikon or even Sony when compared to a CMOS equipped MF Pentax 645Z.