In your sample, +3ev on the 5Ds is actually slightly worse than +4ev on the D810.
If you scroll around the image you can find spots where the 5Ds appears better, but you also quickly realize that at any spot it's splitting hairs with differences that could be due to very slight differences in other factors, even just the default color profiles.
And +4 vs +6 look the same, just different patterns of noise.
The D810 noise is worse in the screenshot I posted, and that's made undeniably clear from scrolling around the image. Though again, the 5Ds @ +4 is not as good as the D810 @ +5, which is why I said between 5/6ev.
2stop difference is huge.
Show us. Show us a real world image you've shot where you pushed shadows +4.5ev, +2ev over my 7D shot, and the difference was huge. You've got a 5D4 which should be able to handle that so if DR is so important, so often, and so huge you should have landscape shots that illustrate it.
I'm tired of words from people on this topic. The lack of images
very strongly suggest to me that the people who bring up DR on forums are
not the people shooting wide DR scenes and producing wide DR prints. And that they therefore have no real idea of the relative impact, what it actually means to shoot two cameras 1ev apart, or 2ev apart, or 3ev part.
Again the sample from 7D doesn't prove anything about 5Ds vs D810 comparison.
Again, you've posted
nothing.