The annoyances with the D800 were not a problem for what I mostly shoot, but IQ was my main concern and the D800 had it.
I can work around almost anything except problematic IQ.
There isn't a modern ILC with "problematic IQ." There are some that are slightly better for different tasks, but that's about it. We live in a golden age of photographic technology. We argue over tiny differences that don't matter most of the time, and barely matter even when they do.
That's the cold, hard truth.
I practically went blind studying sample files from the 5D3, A7, and A7R recently. With RAW files enlarged to 36 MP I could barely see any difference while pixel peeping. In print? No. Nor will anyone else unless you label the prints and tell them which has "more" so that their basic psychology comes into play just like in wine tasting. (The jump from 24 to 36 MP sounds like a lot, but is <25% on each axis. You need a jump of 50% or more on each axis to be noticeable. And at the resolutions we're talking about, even then this only happens with extremely fine detail on very large prints.)
As for DR/exposure latitude, for all the debate on this forum there has been exactly ONE test sample shot under identical conditions, the one from Fred Miranda. And if you actually do something crazy like, you know, use the NR sliders in ACR then you end up with slightly better shadows on the Nikon. It's barely evident at 24" and invisible at smaller sizes.
IQ is a wash within a format and even between formats (m43, APS-C, FF) at low ISO unless you pick from the ends of the resolution spectrum (12 vs 36). And even then the lower resolution sensor is still very good, just not able to print as large.
Heck, even the 1" sensors from Sony and Samsung are excellent at low ISO!
You will not be missing shots on a D810 that you would get on a Mk3, Rather the other way round.
You're not going to miss shots on either unless the 5D3 happens to catch the one frame you want at 6 fps vs. 5 fps, or the D810 at 7 fps in crop mode with the grip. And that's doubtful either way. A 1DX might nail shots you want that these two miss, but 1 extra fps is...1.
And this 'Canon lenses are better than Nikons' fairytale that is spoken like it's fact round here?
Pretty much every lens manufacturer has excellent, good, and crummy glass. I will say that Canon has the most capacity in terms of design and manufacturing, and they are getting wicked good at producing glass that has excellent IQ and is dirt cheap. But basically you can accomplish anything you could want in Canon or Nikon, and 99% of anything you could want in the other mounts.
85mm? Nikon 1.4 and 1.8 are more modern and better than the Canon equivalents which were released sometime during the 2nd word war it seems.
The 85 f/1.8 is a modern design, fast focusing, with excellent IQ and bokeh. The Nikons seem sharper but have horrendous CA wide open. Meh. There are so many 85mm options now from 3rd parties that it's silly to even debate these.
I doubt it on here when 2-3 stops of DR is not desired by anyone it seems.
From the ONE test shot sample we've seen so far in...a half dozen?...threads on the topic that shall not die, DR is nearly identical with an edge to the D810 on exposure latitude. Oh my, better sell all my Canon gear
DxO scoring is used dog food. That and "comparisons" where the tester turns off all NR on the Canon file are what's driving this nonsense.
Same with the 50mm range, except who'd get either a Nikon or a Canon when the Sigma 50m Art is so amazing?
The Art is sharp, sharp, sharp...but the bokeh can be...odd. I actually like the previous Sigma 50 better and I'm sticking with it. The bokeh is stunning on that one.
Nikon 14-24 F2.8? Stunning lens that Canon has no answer for.
16-35 f/4 IS. (It took them long enough.) Now let's see an answer for Canon's T/S lenses.
My point is that this assumption that Canon lenses are superior is uninformed at best and delusional logo fandom at worst.
Kind of like assuming and arguing over and over again that Exmor has 2-3 stops more DR