It depends. 10fps difference in the range 30 to 60 fps can be easily noticed. But it gets less noticeable above 60fps. But I can still feel a difference between lets say 65 and 85fps....mostly if you move quickly around a player character in 3rd person few (for example in RDR2). But that difference is absolutely neglect-able in non-competitive single player games.
Also, important to remember. I believe the actual performance difference between the two cards is about 7% if you compare same games, same settings without ray tracing. If you play a game with setting that produces around 60 fps average, the difference would only be 4-5fps more on the 5700XT. So no big deal.
I would go with the 2060 Super. Performance is slightly lower (see above), but
- you have the possibility of ray tracing. the future is ray tracing, next gen PS5 and Xbox will have ray tracing, the upcoming AMD Navi2 cards will have ray tracing, more and more AAA titles will have ray tracing. I just would afraid of potential buyers remorse if I would buy a card without ray tracing at this time. even so, and I admit, its still a technology in the beginning, but nevertheless pretty cool! And I personally hate it if I can't activate available graphic settings because my card doesn't support them.
- You get much much better and more frequent game optimized drivers from Nvidia. Even so AMD got much better with their drivers....still not perfect.
If those 2 reason don't tickle you at all, go with the AMD 5700XT. It is definitely a great video card as long as you really don't care for ray tracing and the stable drivers. But the slightly lower fps on the 2060 Super shouldn't make much difference.