But such arguments have to be made in comparison of specific formats as applied to particular purposes; the desire to show that "bigger/smaller is always better" seems quixotically futile.
Agreed! But I think I'm covered on that account since I've already acknowledged earlier in the thread (somewhere) that one should always try to use the best tool for the job. This exercise for me has been an attempt to try and get a handle on the fundamental issues regarding image quality alone, as they apply to different formats.
Jonathan made the point that the only 'ultimate' advantage of the larger format is greater dynamic range as a result of the collection of a greater number of photons through longer exposures.
If that point is correct, then all advantages of the larger format will eventually be wiped out with the introduction of that new technology you've referred to, whereby small photodetectors are repeatedly filled and discharged during the course of one 'longer than usual' exposure.
I'm uneasy with such an explanation because; if we look at lens performance of the most popular (historically) of all formats, the 35mm format, we see that it's difficult to find a lens that's truly diffraction limited at f8, never mind f5.6 or f4.
If we go down the scale from large format to very small format at equivalent diffraction limited apertures, each potentially capable of producing the same resolution and DoF, provided the sensors in all cases have sufficient pixels, we get something like the following:
8x10.....f90; 4x5...f45; 6cmx7cm...f22; 35mm...f11; APS-C and 4/3rds...f6.3; 2/3rds P&S....F3.
The above are of course approximate figures, but I don't believe they are far out. The essential principle is, as I understand it, each of those apertures will potentially provide the same 'picture' resolution and DoF provided the lenses are diffraction limited at those apertures.
Now the question I'm asking is this. Which of those formats currently have lenses available that are truly diffraction limited at those apertures? My guess is, only the first 4 (8x10 to 35mm).
Supposing we stop up by 2 stops in order to double resolution whilst still maintaining equivalent DoF across the formats. We get:
8x10... f45; 4x5...f22; 6cmx7cm...f11; 35mm...f5.6; APS-C & 4/3rds...f3.2; 2/3rds P&S...f1.5.
Now I think already we've eliminated all the small formats from competing in terms of 'picture' resolution because there aren't any lenses for those formats that are diffraction limited at those apertures. We are left with just large and medium format.