" Okay, I know that the gold standard for digitizing sheet film in 5x7 ... (snip) "
Hi Clay
I think the diversity of interest and ambition here precludes a 'gold standard'.
It's well demonstrated that perfectly glorious and succesful work can be done from an inexpensive scanner ( like an Epson 4990 ). True, our enlargements are limited, but how much of a handicap is it to make no larger than a 16x20 platinum print ? For a photographer more interested in form and volume than in extreme detail, there is no limitation at all.
On the other hand, if one is shooting LF chromes to make 30 x 40 inkjets,
one needs a different scanner. OR, if we are scanning many images at a time, a big flatbed can be useful.
I think the only standards we have in photography are those which are helpful for the individual craftsman to produce good work.