I think the lack of people talking about bit depth is surprising, I think it should be the main thing to consider, more so than mp. I'd much rather have 16bit version of 5dmkiii than a 14bit higher mp camera. It's the main aspect I'm considering investing in medium format.There is much debate about the "16-bit myth." From what I've read on the matter, I don't believe that a 16-bit camera would produce any tangible improvement over a 14-bit camera, because those extra bits are not actually doing anything useful, just quantizing noise.
I don't mean to say the difference is enormous, and it comes down to it being a small/modest development, but I have seen many examples of medium format 16 bit sensors delivering beautiful, more natural skin tone renditions due to the ability to capture more colors; I've noticed for a while dslrs often have a somewhat, and sorry for maybe not describing this appropriately, but, plastic tonal renditions from light to dark especially over skin tones (the range of tone seems flatter, local, less subtle variations).
Much like every iteration of cameras today, once you have that little bit more/better/broader range of information/techinik, you are happy to have it and will notice the difference the more you use it.