I feel, every time that this subject is discuss, " DSLR vs MF", is more like trying to compare oranges vs apples. It is much more than ISO.
There are a lot of questions that need to be ask for each time someone need to decide regarding to choosing his system.
Purpose of use?
If someone looking to get the best of IQ, richest colors, higher DR and more flexible RAW file, he need more information as start point. Most of the MF back files that I have been test they have more information in the RAW as a start point (less saturated color, less noise in lower ISO and less digital "ironed" image).
Then, what is your budget for the whole system (included optics)?
Someone that has limited budget, might be better to have Sony A7r2 rather than a very old back or poor optics.
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Finally, he need to be able to conclude all the advantages and all the disadvantages of each system and go for the one that gives him the best suited for his use. Someone will go on MF system that included 1/2 optics and it will be enough for his use. Someone else need more optics and prefer the lighter and portable system because he is a journalist photographer.
Today I have both system, DSLR + MF and I think that neither one is absolute better than the second one. Sometime I use the DSLR for most of the ordinary work (web files) due to its benefits and the lower cost (both equipment and time to effort), and sometime I do use the MF due to its benefits (large prints, better IQ, finer RAW output and etc).