A friend of mine loves his D700 and wont change to a 800/810....so I took a fit all lens a Samyang 14mm and looked at the sharpness ratings with a 700/800/810
The D700 rated at 11MP ..well its only 12 so you cannot go over that ....
The D800 rated at 20MP ( thats the camera I use the 14mm on)
The D810 rated at 27MP so that shows the effect of better processing and no alaising filter..
Same lens on a 22 MP Canon 5D 111 ..15 MP so we are not changing to canon are we . No figures yet for the 50MP Canon.
Doing the same test with a D600/610 gives identical figures for each which might tell you something.
Similar results if you try this with a 50mm f1.8 Nikon but clearly not able to check out canon.