390 performs better on 1440p,and there was no mention on which resolution he plays on,so consider it as an investment for the future.Maybe he will someday buy a 1440p monitor if he does not have one already.
Also one thing i noticed,better get a retail version of windows than oem so it's not tied to one computer and you can use it on your future builds.
Edit.Besides the 390 is cheaper,but if it has to be 970 then i would consider an MSI card over evga.