As I predicted, you found out that the two cameras give very similar results at the pixel level. This is no surprise: if you design the test so that:
-the subject has the same size per pixel
-the optics are used in a way to minimise aberrations
-processing is the same
-colours are matched and
-there is enough light and not too much dynamic range,
you will find out that all cameras give similar results at the pixel level. The simple reason is that the only difference would be the presence or absence of an anti-moiré low pass filter. The test is designed to make all other factors equal.
But what you don't see from the pictures is more important:
-the H3D has much better and much more accurate AF, I must use live view on the D800 to come close (this was a real surprise of mine)
-the Hasselblad lenses are much better and perfectly usable wide open. Nikon does not have a prime coming close to the Hasselblad 28mm (which has about a 21mm equivalent FOV on the H3D-31). The 12-24 is Nikon's best wide angle lens. The only alternative would be the Zeiss 21mm and the Hasselblad lens is still better and has AF. Lenses always have been small format's Achille's heel
-the H3D has much, much better colours out of the box, especially skin colours. Sure, I can spend an hour to tweak the Nikon's output to look better, but for a pro in fashion, the capability to output perfect skin colours without effort is invaluable.
-the H3D is much easier to shoot tethered, which is again invaluable for many pros (most of them shoot catalogues pictures)
-medium format will make limited depth of field look nicer, which is essential for portraits. The reasons here are complex, I may come back to that later
-and of course recent MF cameras have much higher resolution.
Sure, the D800 has other advantages. I am not listing them here not because I want to minimise them, but because we all know about them. The point is that your "test" does not show all the practical advantages that count to people who buy MF cameras, because of the way it is designed.