I'm afraid I can't compete in this discussion as far as the math or physics goes, however I found that shots I had taken using a Mamiya 645 with a 210mm lens set at f32 were incredibly sharp and easily beat similar sized 35mm prints shot at f8 (same technique, great glass, blahdiblah and yes I had knocked it of f22 by mistake!).
I was very suprised at this, but to me it makes sense. At 18X12" 35mm runs out of steam, therefore this could be said to be a pretty large enlargement of the frame, which will show any faults and problems.
645 however handles a 16X12" print without even getting warmed up. It is not at the enlargement stage yet where faults will show, or at least make problems.
To my mind, although there may be the same diffraction at f32 on both medium format and 35mm, the diffraction will only show up as the same if you magnify the image the same amount. If you magnify a 35mm frame by X to get a print size where diffraction is noticeable and a problem, you have to magnify the med format print by the same X before you see the same diffraction. The med format print will of course be much larger.
35mm can only be enlarged so much before it gives up for multiple reasons, sharpness being only one of them. I can therefore enlarge a med format frame more than a 35mm frame, and still not have reached the X point where diffraction is a problem.
If I can enlage med format more than 35mm, even for digital, then med format is better for prints over a certain size despite having to stop further down. I'm sure this is even more apparent with 8X10"!
Of course the mathematicians may say I'm wrong, I'm just looking at the prints.
Mamiya 645 210mm f32, every single twig is razor sharp on a 16X12" print...