Detail.
To resort to the anecdotal, derided in these pages some time earlier, I look at my own experience. Nikon and Hasselblad gave much the same detail in the circumstances in which I found myself working. The general max. size I ever needed for most things printed perfectly well onto 10"x12" paper, from either system (as seems to be true today with digital prints on A3+ from either type of digital camera). For larger work, such as full- or half-page press ads and fashion show and shop displays on 40"x60" paper, either camera was as useful because the working distance - the viewing distance - was relatively great and detail was resolved much the same way. What was rather different, though, was the tonality.
Tonality.
I assume the dxo question about it was posted in jest, but if not, it displays one of the current problems besetting photography today: snappers abrogating experience for the illusion of mechanically/electronically measured values which you can't always get; I wonder about the dxo rating of Caravaggio or even dear old Vinnie van G - can't be measured? can't be valid, then. Interesting take on life, my friend.
The definition of tonality that I grew up with was fairly simple: it's the quality of the visible and uninterrupted continuum of a grey or a colour that is not broken down by the failures of the medium upon which it is created. Tonality and grain are the usual suspects here, and both are the unavoidable factors that produce the quality of tonality as well as its failure. Judgement of tonality depends on a trained, experienced eye that understands what's possible and where it is either maintained or lost. That said, even the untrained eye should be able instantly to detect the differences in tonality in two similar sized prints from two very differently sized negatives or positives. The trick, of course, is having the skill to make judgement calls when confronted with a single print and no comparator.
Rob C