I am in the market for a new body as well and started out considering the 5D3 and D800E, then as I learned a little more I threw the 6D and D610 into the mix. Being a retired engineer of 38+ years I tend to be a bit anal about opinion vs objective data and go with quantifiable analysis as opposed to "Uncle Billy Bob takes the sharpest photos you could ever imagine with his Kodak Instamatic and he told me ....".

I read all the reviews I could find on all four bodies. There were a few sites that provided side by side ratings and much to my surprise the D610 was preferred over the other three bodies in all of them. To be certain, the ratings were a mix of objective data and subjective opinion, but in those cases it was qualified opinion by professional experts who make a living doing those evaluations.

Then I did some comparisons using the DXOMark lens test tool using each maker's 24-70 mm f/2.8 lenses along with a few others, and found the D610 performed as well as the 5D3 and D800 in overall score and sharpness. It wasn't until I compared exotic lenses like the Zeiss Distagon T* Otus where the 36 Mpx of the D800 showed a significant advantage. Even with the Nikkor 85 mm f/1.4G the D800 and D610 performed essentially equal. I can only guess from those evaluations is that the current lens technology, even for the body maker's premium lenses, is not adequate to take full advantage of a 36 Mpx FF sensor.

Now I have heard the D800 is a "harder" camera to shoot. I do not understand that one at all, perhaps someone would care to explain. And file size can be an issue; the D800 RAW file are 40 Mb and TIFF files 100 Mb. I do have a 1 Tb drive on my computer, but 100 Mb files can add up pretty fast, so you may want to think about that.

So now the real question is performance vs panache. True the D800 has a full magnesium body vs the D610 polycarbonate front cover, and the D800 can save in TIFF format and 4x5 perspective while the D610 cannot. And the D800 has an allure and probably a few shooting options that the D610 is missing. But the D610 is going to perform basically as well as the D800 and save you enough money to buy another good lens.

If price is no object, you absolutely have to have the D800 name, will be doing some exotic shooting where 36 Mpx vs 24 Mpx may provide you some advantage, or are shooting BIF or wildlife at long range (though a 24 Mpx DX would probably be better there), buy a D800. If none of these are a consideration, a D610 will probably suit you just fine.

A very valid point, you could crop out 1/3 of the D800's image and still have the same pixel count as a D610. However, referring back to DXOMark's essentially equivalent PERCEIVED Mpx data, will the D800's cropped pixels be as sharp as the D610's uncropped pixels? Or to look at it another way, by cropping out 1/3 of the D800's pixels you are also throwing away 1/3 of the light data originally collected, and the D800's photoreceptors are 2/3rds the size of a D610 photoreceptor. Will both printed images still be equally sharp and accurate?

Houdel;
I had a similar feeling when I looked over the specs. While we shoot a lot of wildlife (and crop considerably) we've been getting very good images from our 10 & 16 MP cameras. They have been at least good enough to bring home a bunch of ribbons from local (print) nature photo competitions. A step up to 24MPx may prove to be a major boost in IQ.

Most of our work winds up in a 1024X768 or 640X480 image on a website. We frequently make 8X10 prints and occasionally a few 16X20's.

Ah. Is the button layout like the D7000?

I hated the button layout on my D7000. I like it on the D800. It may be an individual thing or getting used to it, and a trick I learned on the D800 that I hadn't yet learned on the D7000.

My problem with the D7000 layout was that you had to everything with the buttons and the little green screen. I frequently couldn't see the little green screen without putting on my reading glasses. So I found it frustrating.

The D800 has better button choices for me (although I don't know why they make a white balance button) and only one thing on the green screen so that I can see it better without reading glasses. Plus I learned to program the on/off switch to turn on the LCD when I push it to the light...so I can see the settings on the LCD directly if needed. Maybe I could have done that with the D7000?