The DR difference is real between the two cams. I can already see the noise and banding on the building on the left. The Nikon would not produce that banding or close to that level of noise if shot at a low ISO. Here is an example I did for fun when my stone did not fire. This was PRE d800 and was done with a d3x. I think you will get the idea. The d800 was even better. DR aside there are many other things that make a great cam. I really like both the MK III and D800 yet I find myself shooting the Canon more.
