How many? WWhat's the sample area? Worldwide? NYC only? Rural parts of Indiana? Urban parts of Indiana? Are you just asking this of the participants of this forum?
If someone else is buying, the Hassy. Then I could sell it and buy a new car or two. If I'm buying? D800. No way could I ever justify $40K for a camera.
Depends on target audience. Hassy for general shooting is really painful experience.
D800E is "all-around", you can shoot anything you want with it. Hassy is "put it on tripod" and hope for AF to lock (and that you have sensor aligned) and theres enough light.. etc. Hassy is "portable" camera. In same sense 8x10 film was.
25:75 at best.. Image quality from medium format is great, sure, but most people would change mind after few days, or much sooner. But theres Pentax 645D and Leica S. Those I would take over D800E any day..
If money is no object, then the Hassy and a squadron of porters to carry it and all the nice heavy lenses, anywhere I go. They can fetch a triple Americano for me once in a while too.
For me, the D800 is as large as I want to go. At least there is room for a little food and water in my pack then. That wasn't the case when I carried just three large, heavy, medium format lenses and a body. Mind you I could now sneak a sandwich in where film used to be stored in my pack.
I've been wanting a medium format camera for a few years now, so I'd definitely go for the Hassy. I have a D800 and while the sensor and resolution is great, it's still 35mm and has the look of 35mm. I'd go right back to a D700 or a D600 if it meant that I could get a medium format camera as well.
Certain cameras force you to shoot a certain way and that's something I really enjoy. I bought a Fuji X100 not too long ago and it really lends itself to casual shooting and being carried everywhere.
If I'm buying? D800. No way could I ever justify $40K for a camera.