Currently on linux, modern AMD cards have the "best-of-both-world" driver support.
Nvidia currently only produce closed-source drivers.
(Nouveau is exclusively the work of reverse engineering. Recieving nearly no support from Nvidia, except for the occasional patch to enable modesetting)
AMD provides a hybrid stack:
- they develop an kernel module (amdgpu) which is available up-stream. (i.e.: new versions of the kernel feature it out of the box).
above this, you have two choices:
- AMDGPU-Pro, the closed source drivers (which are the modern day equivalent of the user-space portion of Catalyst).
Nowadays, they seem pretty stable, run games without bugs, and because they require a module which is already in mainstream kernel, they do work even with the latest kernel update. (unlike nvidia's driver which need the nvidia.ko some adaptation in case of variation of the kernel API).
- RadeonSI, the opensource back-end to the Mesa driver.
These are devloped by people of whom some are on AMD's payroll (i.e.: AMD doesn't only provide information, but even salaries for opensource development)
With the Polaris, the driver was available at release day, and has a decent performance compared to the closed source one, and runs lots of games.
That's quite some achievement compared with the early "fglrx" that was buggy as hell, and that's quite some engagement for the opensource community.
As a Linux user, I actually like more the ADM driver situation.