The resolution certainly is not the only parameter to take into consideration in the selection of a camera and it is not the only parameter to judge an image, even on a large print, but it is very a important one for the natural looking of the image.
I did tests with my D 700 Vs D 800 and even if I limit the test to the zoom lenses, the difference in resolution is huge on monitor, but cannot basically seen on A3 print whilst is visible on A2 print, but the soft borders can be seen some time on D 800 and not seen (they are there but they are masked) by the lower resolution of the D 700.
Still with the zoom, in wxample the 70 - 200 VRII, the difference can be seen between D 800 vs D 800 E but I do not think that it can be seen on the paper unless you really print very large size, more than A2, and you are really very, very carefull with the sharpening work, a really minor unacuracy can spoil the difference.
Referring to Mr. BartvanderWolf, and I thank him for his post, DxO is performing a very practical measurement, providing the average perceptual resolution of the combination Camera + lens: I am not convinced that the perceivable/actual resolution of normal picture is very different from the perceptual resolution of DxO mesured in lab tests.
I agree that DxO is performing lab tests, and a picture can be quite different, but if at DxO they do their job properly, the lab test work normally is arranged to provide a reliable simulation of the real conditions, at least this is what we were doing us, in my company, performing tests on electooptical systems, including lenses, otherwise the lab tests is not fulfilling the proper job, which is to simulate as much as possible the real standard conditions, and becomes just an added cost, and moreover, making measurements of risolution is not a difficult job at all today.
I agree that if you squeese the camera and the lens with important crops and large prints from that crops you probably get some advantage from 36 Mpx, but, at least for me, this is an uncommon way to gat a picture, I am using mostly zooms to take on camera the proper picture, try to avoid crops ( .... D 700 was teching me along the years!).
What make me thinking that DxO is probably right, is the fact that DxO, basically, confirmas what I found on the field, with no tests on optical patterns, but just with many pictures, normal pictures: in few words the fact that many lenses does not performs well enough for that camera, mostly the zooms, the same lenses that in DxO measurements have a average perceptual resolution rather low, but not only the zooms, even primes.
Anyway, I thank you very much all of you for your attention, for your time and for the clear answers and comments: I will think about more.
Have a nice day and best regards.
Alessandro