I completely agree with you when you say that two formats should be looked differently and dof should also be treated differently like it used to be in the case 16mm and 35mm motion picture formats. As far as Voigts are concerned, the problem that I have observed in various test videos online is how they perform at wider apertures. Its a matter of personal taste. So thats where Nikons come in.
Thanks Guy Mcloughlin for replying, focus is not an issue, have never been a fan of autofocus. I like to work the old way. My main concern is the depth of field and the perspective that I will achieve with metabones. For eg when using 20mm 1.8 with metabones, I will be affectively around 30mm 1.2. Now first of all I dont think increase in light with metabones will make the dof shallower as its just an physical increase in amount of light rather than increase in aperture opening. Secondly the dof will remain of a 20mm lens only despite the fact image size of 30mm is attained. And then its a smaller sensor.