[obican]

 

I had better bokeh with a 110/2.8 in front of the Mamiya 645 than I had with a Zeiss 85/1.4 in front of a Contax/Yashica. Not to mention the difficulties in focussing very fast lenses with only a matte screen in a comparatively tiny finder.

 

That has probably more to do with the lens design than the film/sensor size though. Of course medium format lenses being easier to design and manufacture may help a lot. I was talking about a similar thing with Toni the other night. Everyone says Canon EF 50/1.8 II had awful bokeh with its straight 5 blade aperture, even though most Hasselblad C lenses have exactly the same aperture shape and nobody ever said they had bad bokeh.