I suggest avoiding the AMD RX cards all together(unless they go on clearance). It was one thing comparing benchmarks between AMD & nVidia... but we did a quick comparison at work w/ 2 desktops.
desktop 1: i7-4770 , 16gb ddr3 , 3tb hd , gtx 1060 3gb
desktop 2: i7-4790k, 16gb ddr3, 1tb ssd , rx 480 8gb
We ran Doom & Total War: Warhammer on both machines. Switching back & forth from medium to high settings(at 1080p.. no 4k at work), both seemed to handle the games just as well as the other. Also, the 1060 was $199... whereas the 480 was $279.
We did not do an actual 'fps' check, just wanted to see if we'd notice any difference(visually)
Goes to show that the memory size on a video card isn't the deciding factor... it's the quality of the gpu.