if you want to do some light gamimg and use gnu/linux i would go amd because of the drivers. nvidia drivers are really not so good in terms of SELinux and such. There is a thread https://forum.level1techs.com/t/linux-nvidia-security-discussion/113770
Maybe do wait for Kernel 4.12 and Vega cards, then the RX Series will get cheaper and maybe you can get a better card for the same price?