ajfotofilmagem said:
For shooting at ISO 100, underexposed and raising shadows, 80D is the best of the three.
For shooting at ISO 1600 with correct exposure, 80D seems the same as the 7D Mark ii, considering a 7D Mark ii without any defect...
This.
The consensus of reviewers is that the 80D sensor does not perform any better at higher ISOs, than the 7DII or 70D.
I've used the 7D, 7DII, 5DIII and now the 1DX II. My opinion is that the 7DII was significantly improved over the original 7D at higher ISOs. It was not quite as good as the 5DIII at high ISO, but not far off. The 1DX II is the best, but at higher ISOs we are talking marginal differences. If you are distance limited and need to crop the image, the 7DII can perform nearly as well as a 1DX II, at 3200 and below.
The key to higher ISOs with Canon, I believe, is to avoid underexposure. Pushing shadows seems to invite noise, while a properly or just slightly overexposed (1/3 stop) image does much better. Of course it is a trade off and when you are trying to squeeze the most out of a low light situation, you can't always afford that extra little exposure.
Just my opinion.