Nvidea or Amd, which should I buy

At the moment Nvidea is great, with their "new" 20 and 16 series, But wait a few months and AMD will come out will something, It you plan on buying new AMD for sure, But used, A good 980 ti will set you back 200$ on with better performance then RX 580 and 1060 6 gb. The build also matters, Trying to keep the all AMD style with AMD CPU then get a AMD GPU.