Which used 4GB card to buy? RX 580 or GTX 980

[1405]

I have a chance to buy either card for the same low price from someone I know. Neither card has been used very much. And neither card has been overclocked or used for mining.
Both are 4GB DDR5. It will go in a system with a Ryzen 3-1300X, 16GB RAM, and a Corsair TX650M PSU.
I can't make up my mind.

RX-580: https://www.powercolor.com/product?id=1496737702
GTX 980: https://us.msi.com/Graphics-card/GTX-980-GAMING-4G.html#hero-overview

 

[Dunlop0078]

Which is cheaper? They perform very similarly. The RX 580 will beat out the 980 in a lot of DX12 and vulkan games, however the 980 will win in most DX11 games. The RX 580 will likely do better in future games so I would probably opt for that assuming prices are the same. However I would think with the current mining craze (something the RX 580 is much better at) that the RX 580 would be a lot more expensive even used.