Before we ruminate on the data we've collected, let's summarize that information using our famous value scatter plots. To make our higher-is-better graphs work, we've converted the geometric mean of the 99th-percentile frame times for our tests into FPS. On both the 99th-percentile-FPS-per-dollar chart and the average-FPS-per-dollar chart, the best values will congregate toward the upper left of the chart, where the price is lowest and performance is highest.
Going by our all-important 99th-percentile-FPS-per-dollar metric, both the RX 570 and RX 580 offer nice improvements in delivered smoothness over their first-generation Polaris brethren. The RX 570 pulls on par with the GTX 1060 3GB in our 99th-percentile-FPS-per-dollar measure, while the RX 580 actually surpasses the GTX 1060 6GB for smooth gaming despite that card's higher performance potential (as measured by our average-FPS-per-dollar chart).
We'd have expected nothing less, too, given the fact that the Sapphire RX 580 8GB card we used in our tests made our test system draw 93W more power under load on the way to achieving victory over the EVGA GeForce GTX 1060 6GB. No, that figure is not a typo. For its highest-end RX 500-series card, AMD seems to have abandoned any pretense of competing with Pascal on a performance-per-watt basis. Getting the last few untapped percentage points of performance out of a GPU can require major increases in voltage, and AMD seems to be OK with that extra power draw in exchange for the smoothness crown at the $250 price point.
In turn, builders will need to spec cases with more cooling power and higher-end power supplies to take advantage of the RX 580's high-quality frame delivery. If waste heat and power consumption are prime concerns, the GTX 1060 6GB is unquestionably the better pick.
If the RX 580 demonstrates what happens past the hairy shoulder of the voltage-and-frequency-scaling curve, the RX 570 seems better able to enjoy the fruits of GlobalFoundries' improved 14-nm process tech. Despite drawing just a few more watts than our XFX RX 470 card under load, the MSI RX 570 Gaming 4G we tested achieves much higher boost clocks than its first-generation Polaris forebear, and it has no trouble maintaining those speeds under load, either. Not a bad deal at all for the more wallet-friendly Polaris 20 card. Given the difficulties the GTX 1060 3GB can cause gamers thanks to its meager complement of memory, we'd pick the RX 570 (or any RX 580 4GB card) over the Nvidia competition here any day.
A fuller set of tests might swing the pendulum more decisively in favor of AMD or Nvidia at this price point, but we think we've gathered enough data to say that the RX 500 series successfully closes the small gaps that existed between RX 400-series cards and the Nvidia competition. Depending on how prices work out at e-tail for this highly competitive segment, we think the conclusion is simple: buy an RX 570 or RX 580 if you were planning to buy an RX 470 or RX 480. If heat or power consumption are a concern for you, get the GTX 1060 6GB instead. You really can't go wrong either way.