AMD is probably the best choice for Linux now, not that nVidia isn't still as fast for gaming, but there are a number of limitations to using both the proprietary and open source nVidia driver, and proprietary is the only option for nVidia if you want decent performance.

My wife had huge problems with xruns due to some sort of bug in the nVidia proprietary driver running with a real time kernel.

Xrun is when the Audio doesn't fill buffers in time, usually it's just a few milliseconds and mostly inaudible, but it's no good, if you are making music.

I'm sure for most either is fine today. But if you want to engage in open source development, AMD is by far the best choice, because the open source driver is much more well behaved, both than the nVidia open source and proprietary drivers.