There are probably cases where the extra .7ish stops of range in the Sony camera is enough to sample a scene for which a Canon camera would be blown out in the sky region. Whether there will be a visible difference in the image of an ETTR capture is unclear.
There would be a noise difference in the deepest shadow regions visible while pixel peeping, and possibly on a large print before NR. With a little NR there wouldn't really be a difference.
Admittedly Canon makes a lot of cameras where you can't necessarily recover the darkest shadow detail due to noise. I've said before on this forum that if I did RE for a living (rather than on occasion) I would probably have chosen a 5D4 over a 5Ds. There are RE scenes that will easily blow out any camera and scenes that would fit on any camera, but in the middle you'll be blending exposures less often with a Nikon, Sony, 5D4, 1DX II, or R.
But the 1DX II is one of the cameras that's very close to the best offered by Nikon/Sony. So close it really does boil down to post processing so long as you ETTR.