I didn't realize this was being talked about here, I posted this initially on the about this site section, anyway, here goes:
Michael, I strongly disagree with your assessment that lower pixel count digital backs are becoming irrelevant because the pixel count increases of digital SLR's. As you say earlier in your article, it's about time people stop worrying about pixel counts and start thinking about quality and in that regard digital backs give a very different look than a DSLR. A 22 MP DSLR is about as different from a 22MP digital back as a 16MP DSLR is from a back, it's not the pixel count that you get a back for (though it can be useful) it's the different look. I'd be surprised if you didn't agree.
Back in the film days I skipped the 645 format and went up from 35mm to 6x7. I found that while 645 offered a slightly different look than 35mm there wasnt as large a difference as with 6x7 (specially when using appertures in the f8-f16 range as I do with strobes) which did offered a significantly different look. 4x5 is still in a league of its own obviously.
But todays MFDB's dont even have sensors as large as a 645 negative let alone 6x7 so the difference in look (from a full frame DSLR) might be more due to sensor characteristics and processing (and lets not forget optics which vary from mfg to mfg) rather than a large difference in sensor format. Its pretty subtle.
At any rate, if you need/want to shoot ultrawide then medium format is a bad choice, was then, is now. For that 4x5 film is great and in digital obviously 35mm format DSLR's from nikon and canon are best due to the available optics.