I've been debating a reply to this thread for a while, but I think I've narrowed it down to two specific cases where I *think* I prefer images made on larger sensor bodies over smaller sensor bodies; either MF > FF, or FF > APS-C for example.
Case 1 are images that are fairly wide angle with shallow DoF, but a razor sharp subject. I can get close to that look with my Sigma 30mm 1.4 (at 1.4 or 2.0 depending on subject-background contrast), but it's not wide enough for my liking. I'm thinking 24mm? Dunno, I haven't researched it, because research is the first step to LBA...
Case 2 are portraits that are moderately tele, say between 85mm and 135mm on FF, again with good subject isolation. I can get close to what I want with either a 50mm or the short end of my 70-200, but I'd much prefer to have the perspective of 85-135mm for portraits. This is one case where random images on the interwebs doesn't help, because it's person specific. Is that persons nose really that big? Do their ears really stick out like that? If it was shot at 85mm, yes. 16mm, probably not... But clients sure can tell the difference when it's a person familiar to them! I should actually sift through my clients selects and see if there is a preference for longer focal lengths... hmm...
I guess what I'm saying is that I may not be able to tell all the images apart that others have made, but I do know the kind of images that I'd like to make, and I don't think it's as easy as it should be on APS-C... and very similar to the prior comment that the D800E sets a fairly high minimum bar across a wide range of shooting situations.
Now if I could actually mount my current glass to a FF I suppose I could take similar shots on ...ahem... 'equivalent' glass, and see if I can tell the difference. Then buy the FF anyway