Power, Temperature, Noise
The downside of the Polaris RX 570 architecture, if you can call it that, is higher power consumption than GTX 1060 6GB, to the tune of 43W. Hardly game changing, but may prove to be more relevant if you plan to run multiple cards for mining.
Sapphire's cooler does a good job at keeping temperatures and noise in check; the card could barely be heard under load.