My custom desktop PC started off with an AMD R9 390. But that GPU became faulty within it's warranty so requested I exchange it for a GTX 1070 and pay the difference.
I think GTX GPU's are better. They're popular among the younger players, and they have a MUCH more reliable PVR system to, NVidia Shadowplay. Tried AMD's Raptr and got a bunch of black screen recorded videos, with my former AMD GPU. No problems recording using NVidia Shadowplay. And it's just so much easier to use.
Under my warrant they did give me the option to go for the AMD 480, but that GPU is weaker and has less cores than a GTX 1070 and even an AMD R9 390.