But in real terms, AMD is migrating their proprietary user space drivers to run on fully open source kernel drivers. It'll be an awfully chilly day in hell when Nvidia decides to do something similar.
I'm running a Radeon RX560 (replaced an Nvidia card), using the open source AMDGPU kernel driver and Mesa. It's seamless and works at least equal to (probably better than) the proprietary Nvidia drivers.
I went with Radeon as well because their open source drivers. I am a very happy user. No more bad surprises when updating kernel, which has saved me more time than I'd like to admit, since I used Nvidia because of performance.