You're right, I haven't ruled out the possibility that the older cards were just better and that all newer cards might cause issues. I did dig around in the amdgpu source code and seen that for the most part it's pretty simple to disable dithering through xrandr on the AMD cards. Also the code shows that when you do use dithering, it will choose a spatial dithering algorithm and not a temporal one. And if that ever changes, it's open source, so it can be changed quite easily with patches if need be. Opposed to the Nvidia proprietary driver where you don't know what the hell is going on.
I've struggled with trying to keep Nvidia dithering off. Whenever I change it to disabled in the Nvidia X server settings, and then reopen the settings it automatically resets it back to on, along with resetting a bunch of other settings I was testing. And I haven't seen anyone else mention running into this problem. So maybe it's just this particular brand of GTX 970 that's messed up in Linux, I don't know.
The more I read about Nvidia and Linux, the more I just want to get the hell away from their cards. AMD seems to have been constantly providing updates to amdgpu, whereas Nvidia barely wants to touch Nouveau and just stick with their proprietary driver.
Also with Wayland slowly making progress, it seems AMD is far more ahead with supporting it then Nvidia.