Let me add some "parameters" that you may have never considered...
1. when one buys an "old" (they are never old) MFDB never read an old review of it... Why? ...because its performance has nothing to do with what it can do with modern software...
2. Resolution is almost irrelevant to detail... If one compares a P25+ to an IQ 180 and prints at 4x3 feet (the same capture with the same software), he will hardly see any detail difference that he would consider serious to bother with (unless if he is mentally disturbed as to pixel peep with irrelevant to the art of photography matters)...
3. You'll hardly see any difference (the above parenthesis applies here too) with DR or rendering either...
4. You may find different "looks" between backs and that (IMO) is a key factor for your choice...
5. Forget about using ANY back (CMOS ones included) at above 400 Iso and retain "MF photography looks"... this thing doesn't exist... There are (now) backs that are able to shoot "clean" 6400 Iso... but that's irrelevant as to compare them with DSLRs being committed to job...
6. There is nothing to compare a multishot back in multishot mode for IQ, irrespective of resolution... (applies for stills only).
7. Older backs (up to 50mp with no microlenses on the sensor) are by far better than "modern" backs to use with technical cameras.
8. With technical cameras (ie "real" photography), right shimming of the (analog) VF can be as effective as any LV...
9... (up to 100+ because I'm tired...) You can read more crap on web than anywhere else...
That's (and careful planning) all you need... IMO.
