It depends on your priorities. And if you are only gaming my sole recommendation would be the 5700xt. It has the best price to performance ratio. But if you want nvidia exclusive features like Ray tracing, DLSS, CUDA, tensor cores etc. then go with Nvidia. But get the RTX 2060 super instead of a 2070 because a 2060 super is basically a 2070 in disguise. With the 2070 you might get like 5 more FPS, so go with the RTX 2060 super if your going the Nvidia way.
Hope this helps!!