“So if we have a close race between a 39MP back's files and a 4X5" drum scan, where does that leave us? A traditional enlarger made print can't hope to compare, and so we now appear to have a new ball game, with top-tier medium format digital close to equaling 4x5" large format.”
How does it follow that a traditional enlarger made print can’t hope to compare? Perhaps you were referring to scanned film printed on photographic paper? Prints made from film and enlargers are different and have somewhat different qualities but your samples did not include them. I personally switched from Fujichrome R prints to an Epson 7600 in 2002 and I think that both technologies can produce very nice images.
My work is produced from medium format slide film, mostly Pentax 67 printed on an Epson 7600.