Hmm I see where you're going there, I am a Canon user just to be clear, but have read several times that the newer Nikon sensors have better DR. I don't know this, it is just what I have read.
So do you think the Nikons aren't as good at DR as some claim given your point about the Sony 42mp sensor? Which I didn't know even existed! I am waiting for the 1dx2 or whatever it will be called, had I more money or far less glass I might have given Nikons a try.
I just hope Canon do some justice to us that have waited this long and continue to do so.
They are definitely that good, I shoot a d750 and at Base iso I can push pull 4-5 stops and it's still very clean without banding or noise. Hopefully canon will do something about it as I had high hopes for the 5ds/r but like a lot was disappointed.