For real estate shooting with available light is the name of the game... we can cheat with speed lights for photos but when it comes to video... The D800 doesn't even compare. There are so many dark areas in a home, on the D800 noise covers the dark areas... The 5D Mark III Does a fantastic job. The above teaser admittedly was shot in day light (shoot time was bumped up) but the low light work that we have done... the D800 doesn't compare.
That said the D800 does have more range, but it seemed as though it was just brightening the dark areas to deal with the noise... problem is that sometime we want deep darks in our video.