i think i would be pretty torn if i were to be starting out now between the sony (although the A9 rather than the A7 series) and the D850. Both cameras are absolutely amazing and while i do have a bias to nikon i find the current predicament nikon are in financially worrying along with their lack of innovation. Sony are really pushing the boundaries of late and improving year on year and so they seem like the obvious choice, but having played both cameras its a damn close call for me based on the here and now. I think i would just about go with the nikon as things stand, its the safe bet in terms of lens availability, and what i know, but if i were looking longer term and speculating then i would probably plump for the sony.