Is there any real question that in prints of a certain large size, MF is technically better that other formats, given equal care? I mean, does anybody claim that FF can't be told from MF under any conditions?
This is an actual question, not a rhetorical one.
I shot some dancers in Central Park a few years back. Something I shoot a lot of, but on this occasion I swapped my Canon for a Phase One 65 MP back. The reason, there would be about 2000 dancers in shot shot, not the usual one or two and boy what a difference it made as you can easily recognise everyone whose face can be seen, even way at the back.
Also when testing the back, I took a shot out of a window onto a typical narrow NY back street onto a very brightly lit street with sun overhead. The sun was striking directly onto the roof of a white truck and the windows behind were in deep shade due to some scaffolding. Unlike with my 5D the blindingly bright white roof was not burnt out and the detail in the shadows was not murky and noisy. I was very impressed, much better quality both in resolution and dynamic range - a bit rubbish for fast moving subjects in low light, but that wasn't this job.
Obviously I didn't shoot both with my Canon for comparison, but I did do some portraits a while back on both a 5D and a Hassy 3D. If I remember I'll dig them out and post them here at web size and see what difference it makes, if any.
My girlfriend is a big fan of America's next Top Model and also the truly awful British version. So I sometimes catch the end part and even with the show being shown in 4:3, SD quality, it is really obvious when looking at the final photos whether they were shot on a DSLR or a MFDSLR as the images look markedly different in quality.
My view is that magazines are one of the biggest tests of image quality, not wall prints. You hold magazines quite close, so they fill your field of view far more than a print on a wall or an advertising poster does. The reason is that you tend be further back relatively speaking. A magazine held at reading distance with a full bleed double page spread would equate a 10' wide by 6" high print on wall opposite me in the living room if maintaining same field of view.