I don't necessarily disagree, the cards have the same pure performance, while the rx is around 20€ cheaper!
But the tdp of the rx 580 is around 60W higher (which will void the 30€ difference in around 2 years, and will benefit after), the gtx is cooler and quieter.
But the main point for me are the driver interfaces, amd settings + amd relive vs nivdia settings + shadow play.
Relive is garbage nothing else, honestly garbage. It does not only triggers stuttering and input lag in csgo for example it also doesn't work on some cards (for me it is not working on r290 and hd7870 while it is working on r390) also it has just way less options and a buggy interface. Amd settings doesn't even allow u to change HZ or the monitor setup.....
Nvidia Shadowplay is working on my 780 and my 1060 (780 comparable to r290 from age, just to make that one clear), it almost has no impact on fps, has many options and a clean and well thought interface.