I know Nikon's and Sony's processing is different, but I shoot RAW, so don't look at jpegs much. I did rent an a7riii very briefly, so hard to say for sure, but it was putting out images pretty comparable to the D850. I wouldn't say, OMG, this Nikon-tweaked sensor is so much better. Just from what I've read, it sounds like Nikon is spending an awful lot of time on "sensor design" for very little, if any, gains over an off-the-shelf Sony. Maybe in the past, they were able to squeeze more out of them, but comparing two similar models (D850 vs a7riii) doesn't seem to show much difference.