A couple of comments .
First, Pentax 67 optics don't come close to Mamiya 711. I once owned both systems at the same time and in my comparisons, which involved both real life photography and tests with targets, Mamiay 7II lenses gave between 25-45% more detail than Pentax 67 lenses.
Second, tonality is not uniquely a quality of real estate (area) with film. It also depends on grain and film contrast. Tonal transition values are much better with fine grain B&W films than with medium speed and high speed films. In general if you compare 4X5 and MF film of the same type and speed the tonal transitions will be better with 4X5 at the same magnification. But if you make the comparison between a high speed (ASA 400) film in 4X5 with a medium speed film (ASA 100) in MF results should be quite similar.
Sandy
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