Why wouldn't you buy an Nvidia card? They are pretty much guaranteed to work fine with linux, and since much longer ago. And now, even those dual GPU/CPU laptop cards.
It's the attitude Nvidia show towards linux driver development. You only get a binary driver, so if Nvidia tomorrow decide that linux is no longer for them then you're screwed. Also they downright paranoid when it comes to releasing specs and firmware for new cards, which is why the open source nvidia drivers are so poor.
AMD, on the other hand, is actively working with open source developers and the core of the new AMDGPU drivers is open source and shared by both the kernel version and the AMD-provided binaries. It's got to the point now where the open source drivers are a viable option for playing games, along with the big strides made by the Mesa openGL drivers, and that's down to AMD. If I wanted to send a message to graphics card designers that I prefer this attitude then I would ditch my old Nvidia card and buy one of the new Radeons, which is precisely what I did and I don't regret it. They may not yet be on the level of the Nvidia drivers but they're heading very rapidly in the right direction, whereas Nvidia couldn't care less.