Petie53 is one generation behind. The 7D2 is, and the 6D2 will be, weather-sealed. As he states, no Canon DSLR is totally sealed.
The 80D (aps-c) is hugely better at high-ISO than any other aps-c Canon body. The 6D (best-high ISO Canon body when it was new... 5 years ago) is less than one-stop better. The 6D2 should improve on that. The 6D is (very) slightly better at high-ISO than the 5D3. The 6D & 5D4 can AF at -3EV; the 5D3 at -2EV.
Canon has been making strides in sensor dynamic range, and high-ISO abilities lately. For what I do with a camera, ISO is no longer and issue. I don't mind shooting my 80D at 16000, or my 6D at 25600, when necessary. I like a lot of the new features on my 80D: anti-flicker, killer AF, DPAF for LV & video, flippy screen. Canon does not currently sell a camera with all the combined features of the 6D & 80D. The 5D4 comes close; it lacks the flippy screen. The 6D2, to be released in about 10 days, does offer all the combined features of the 6D & 80D. The only thing that concerns me about that body is the AF-point spread.