When you are purchasing a camera, you are not just buying a body, but are buying into a system. The body is important, but the lenses are much more important and more expensive. Then, there are accessories like flash, and be sure to look into manufacturer support and service turnaround times.
I bought a D800 along with a few high end lenses. At ISO 100 the camera is truly impressive, as ISO increases, there is less DR and at about ISO 800, I started to be disappointed, but it is fine with a lot of NR.
Thats where the problems begin. NR processing of large files means wait, wait, and wait. I took 500+ images at a low light event, and DR was poor, and processing took several days.
I also found that Nikon has yet to have but a few lenses that can match the sensor.
If you are taking landscape images at ISO 100 and have the top lenses then I highly recommend the D800. For all around use, it is a struggle, particularly if you use raw and process a lot of images.
So, it is great for some and frustrating for others. I won't recommend either, but be sure you price a entire system and make sure you have the fastest computer available with a ton of memory.