Hi,
Now that Canon has the 5Ds/5DsR I cannot really see why Canon users would use an adapted A7rII for shooting things like birds in flight or sports. Canon has the camera for that.
For those needing high DR the Sony A7rII may be attractive.
Best regards
Erik
Nikon/Sony Exmor sensor cameras only have an big edge in image quality mainly if you shoot at base iso or below iso 400. Once you start shooting at iso 800 and above it makes little sense for a Canon shooter to switch.
The A7RII looks like it has raised the exmor image quality noticeably so it might b the holy grail of sensor measurebators. I am sure it will score well over 100 in the DXo test. We will know in a week but I suspect that once people start posting image quality tests of the A7RII it will shake up the camera world. I mean, lot's of people are still gonna be making lot's of crappy pictures with it, just like with any camera, but it will be a great tool in the hands of someone who know what he/she wants and knows how to do it.
I played with a few low iso raw files and the depth of the files is just stunning. I was pulling clean detail with good color out from under a sofa in a well underexposed, backlit! image. As good as the D810 is (which IMHO is an improvement over the A7R and D800E) the A7RII is gonna wipe the floor with every sensor ever made in regards to base iso DR. It also should push high iso performance even higher.
Where the 5DSR might have an edge is in detail and also long exposure image quality which has been talked very little about but is a HUGE improvement over the 5D3's.