Ok. So I guess this is obvious by now... We have different perspectives based on our objectives and ancillary equipment. You are right, if you are focused on traditional requirements, and they do not include large prints, large display, or how they will hold up on future devices, then yes, not much different. But I don't think like that. That is not the world i lived in five years ago or now. I have photos back to the 1950's and the older, and better quality they are, the more I appreciate them. We are taking photos now that, hopefully will be seen in ten, twenty, potentially much longer ( preservation should now be much easier). I have said my piece about future display devices, hopefully this is a valuable perspective to those not lucky enough to to be a bit closer to the leading edge. Anyway, from my perspective there is a big and instantly noticeable difference between the two cameras.
When I got my D800. I went outside and snapped a couple photos in my neighborhood. Took it in and popped it in Lightroom. I noticed a couple specs of dust in the sky. I said to myself, "Darn dust is going to be a real problem with this camera." I was really disappointed. The sky was very white, and the lawns and trees were black (silhouette), I clicked the darkness slider and the landscape snapped many f stops into perfect exposure... My jaw dropped... I could never had done anything like that with my D700... Or D200. Anyway, For some reason I hit the 1:1 button and saw the dust specs... Two geese! Clearly their head, neck, body, legs and feet! Their body color visibly different than head and neck. Just for fun I made a 8.5 by 10 print to show my wife... The dust specs, an one at 1:1. This day changed my life, clearly this camera is leagues ahead of previous models. I had a preordered D800, so have had it for over a year... However long they have been out. It has been an amazing world of discovery and amazement. I occasionally use my D700... And kick myself each time I do. I can't click on the Lightroom button to go 1:1 and see if I know that ant... I mean person in the corner of the photo. So if confronted with a D600 vs d800 decision I would recommend the D800... It is more future proof. aLthough both are very capable.
I also shoot two APS-C cameras, and have learned how much you have to tweak each workflow to get the most out of your photo depending on the source. Like sharpening. I can make a APS-C photo look sharper than a D800.
Anyway, from my perspective and experience there is an order of magnitude difference between those two cameras, they are not in the same league. You are also correct, from your perspective.
Think I forgot the topic.
JD