Here we are comparing two cameras with different body types: Sony A9, which was introduced in April 2017 is a Pro Mirrorless camera with a 24.0MP Full frame sensor whereas Nikon D810, which was introduced in June 2014 is a Semi-Pro DSLR camera with a 36.0MP Full frame sensor.
Despite some fundamental differences of these two body types, Mirrorless cameras are becoming serious alternatives to DSLR cameras thanks to their size/weight advantages and recent improvements in their focus speeds , which makes this comparison even more interesting. Fortunately, you can't go wrong with any of these cameras as we rank them amongst Top 10 cameras in their classes. Sony A9 is ranked #8
out of 39 Pro Mirrorless cameras with an overall score of 93 whereas Nikon D810 is ranked #6
out of 90 Semi-Pro DSLR cameras with an overall score of 87.
Let's have a brief look at the main features of Sony A9 and Nikon D810 before getting into our more detailed comparison.