I received my 5DsR yesterday and couldn't wait to compare it to my 7D MkII at ISO 400 and 800. Those are my typical bird in flight ISO settings, in order to get a high enough SS. I mounted my EF 500mm f/4L IS II on my sturdy Induro tripod and took pictures of a sign with a great bit of detail (look at the edges of the letters). The exposures are the same for each body at each ISO and well lit, not challenging either sensor. I let DxO Optics Pro 10.4 apply Default noise reduction and sharpened the Raw images all the same in conversion to JPEG. It's interesting see a slightly different color interpretation of the two bodies.
Interestingly, the corrugation of the sign's surface didn't cause moire in the 5DsR.
All my wildlife shooting today was with the 5DsR and, of course, I discovered quickly how much slower the 5DsR is and filled up the buffer once or twice and it took quite a while to clear. Given the results of this test, the 7D MkII will remain my bird and wildlife body and the 5DsR will be a most excellent portrait, travel and landscape body. I was very pleased with both bodies, but actually a little surprised that the 5DsR didn't show more difference at ISO 800. I'll look for a repeatable target with finer detail.
You can see full EXIF at the Flickr site. Here's an Album on Flickr showing all the cropped and uncropped images: https://www.flickr.com/photos/dcstep/sets/72157654706175433/with/19820296814/
5DsR at ISO 800 cropped to 1316p
5DsR Cropped To 1316p ISO 800 by David Stephens, on Flickr
7D MkII at ISO 800 cropped to 1316p
7D MkII cropped to 1316p ISO 800 by David Stephens, on Flickr
5DsR at ISO 400 cropped to 1316p
5DsR Cropped to 1316p ISO 400 by David Stephens, on Flickr
7D MkII at ISO 400 cropped to 1316p
7D MkII cropped 1316p ISO 400 by David Stephens, on Flickr