This has been my experience, I wonder if others have felt the same.
AMD's GPU drivers have been perfectly fine since the 9700 Pro. That's a 16 year old myth at this point, let it go.
The few games using OpenGL on Windows I can find show AMD's performance being perfectly competent:
https://www.pcgamer.com/doom-benchmarks-return-vulkan-vs-ope...
https://www.hardocp.com/article/2014/05/21/wolfenstein_new_o...
The nvidia cards were on average a bit faster, but that was true in DX as well. Meaning it wasn't just "lol amd opengl drivers"
And of course Linux testing, where OpenGL is far more common, shows no major disparity, either, which you already know hence the qualifier of "on windows" but that qualifier makes no sense. It's going to be the bulk of the same code between windows & linux for the driver, as has also been rather well tested & verified.
Which gets back to "it's a goddamn 16 year old myth" that literally spawned out of Nvidia's hyper aggressive opengl optimization of Quake 3.
I’ll take the word of a well respected former ATI employee.
ATI started rewriting their OpenGL driver in 2004-2007. Long after 9700 Pro’s prime.
As told by the author, it was a long lasting disaster.
It's an interesting story of project management nightmares, but it doesn't provide any argument to the state of AMD's drivers as experienced by end users either way.
In terms of stability we do have some large-scale metrics on that front, such as Vista's crash blaming. Those metrics don't support claims that AMD's drivers are less stable than Nvidia's, as the Nvidia was responsible for 28.8% of Vista crashes while ATI was 9.3%. Given more Nvidia than ATI users that's not necessarily damning, but it also clearly disagrees with the notion that ATI is deeply unstable while Nvidia is rock solid.
And keep in mind during the 9700 Pro's prime all the way up to today OpenGL is used by nearly nothing on Windows. We're already talking about the niche use case.
The ATI dev on twitter made no such claim. In fact he never made any claim about stability at all. Just that the new driver was missing functionality, so only specific things (like Doom3) got it and they were shipping 2 OpenGL drivers as a result during 2004-2007. End-users weren't broken during that timeframe. The old driver didn't suddenly break and get super unstable. If anything the complaint is that the old driver was too stable, it wasn't getting new features & changes fast enough.