My significant other has a Canon EOS 600D, I have a Sony NEX 7. We would like to consolidate, i.e. purchase one (better and more up to date) camera we share. We've had a discussion about which system to go for, and she's made it clear it's important to her to stick to a camera with mirror and she prefers the handling of the Canon, which means staying with Canon and getting rid of the Sony and the E-mount lenses.
I'd like to surprise her with a new camera for Christmas, but am unsure which EOS model would be the best fit for our requirements. I have looked at the 80D, 7D mark ii, 5D mark iv and 5DS in detail. I would expect a new purchase to carry us through at least the next 5 years without getting the feeling we should upgrade again.
Our main use cases are:
For her job, she frequently has to take pictures of building sites and the interior of houses and flats. She's always complained about missing a wide angle lens (we will get one). A tripod is used about 60% of the time for these pictures.
Also for her job, photos taken by us frequently end up in newspaper adverts and large banners hung outside building sites. While the 18 / 24 megapixels of our cameras have so far been sufficient for the purpose, I suspect having more will enable her to be more free in her ad / banner designs.
During our travels, we take pictures of landscapes, people, plants and animals. We do occasionally have posters printed of photographs we like and hang them in the office.
While high speed photography has never been really important for us, there's a fairly good change that nephews/nieces will be around soon, and while toddlers usually aren't lightning fast, it would be nice to have a speedy auto focus and serial rating.
We own the following lenses: EF-S 55-250, EF-S 18-55 and SEL1855, SEL16F28, SEL30M35, SEL18200 - the SELs we will get rid of and purchase corresponding EF/EF-S lenses (I'm going to miss the SEL18200 though).
The 80D and 7D mark ii are the cheaper ones I've looked at. I believe they would still cover quite a lot of our requirements. What deters me is that 5D and 5DS seem to have much newer technology, and I'd love to have a full frame camera. The 5DS and 5D are on par in terms of price, and it's obvious that the much higher resolution of the 5DS would allow huge posters/ads/banners - yet it is marketed as a specialist camera and I wonder what the drawback is. The 5D seems a good choice - but then there's the doubt about the lower resolution compared to the 5DS.
I would much appreciate an answer telling me which model would be best choice for our specific requirements - I do realise that this question is somewhat open to opinion, yet I hope I've made the situation clear enough to allow for factual answers (and avoid getting the question closed).
It has been suggested that this is answered by another question, which provides a general overview of the differences between EOS cameras. While this is helpful information, I fail to see how it answers my question, which is which of four models most accurately fits my specific requirements.