If you buy Nvidia, you'll be stuck with their weird proprietary drivers and miss out on neat shit like Wayland and kernel modesetting (really useful for RetroArch).
Mostly depends on what you wanna do. Some around here lament having bought something powerful, only to end up playing low spec indie titles and emulators.
I'm on a AMD 7970 here and play mostly emulators recently. Breath of the wild ran 1080p with 60fps locked, Persona 5 runs 30fps locked. (60fps patch fucks stuff up) Nier Automata after that fan patch came out ran 40-50s maxed maxed out without AA.
So really I don't see the point of upgrading. Invest in a freesync monitor and those 40s to 50s suddenly feel like great smoothness.