Druidsmark :
This is an unfair test since the XFX Radeon RX 580 8G 2048SP has a clear advantage over the stock GeForce GTX 1060 3GB. The test would have been much more fair and accurate had they used a stock GeForce GTX 1060 6GB card. The GeForce GTX 1060 3GB card does not enough ram to run games at ultra high graphic settings at 1080p, at least in some cases as I have the GTX 1060 6GB version and I have had the rare game tell me I need more ram if I want to turn up the graphics in games at 1080p some times. If they want to do an honest comparison of the two graphics cards it should be redone as Radeon RX 580 2048SP vs stock GeForce GTX 1060 6GB card at 1080p for gaming.
How is it "unfair" that the Radeon card has nearly 3 times the VRAM for the same price? As has been said, the 1060 6GB and 3GB are not the same card, as the 3GB version has 10% of its cores disabled, similar to how the RX 570 / RX 580 2048SP is a cut-down RX 580. If Nvidia wants to cheap out on the VRAM but still charge just as much for the card, that's their own fault. This is a more than two year old card that is still selling for at about the same price it launched for. Some games already show performance limitations from having only 3GB of VRAM, and that will only cause more of a performance impact in the future as game requirements climb. That's not to say that the 1060 3GB is a bad card, and it does at least have an advantage in terms of power draw under load, but it's only fair to compare cards against others in the same price range.
And on that note, at online stores in the US right now, it's possible to find the RX 570 (even the 8GB version) for about the same price or in some cases less than a 1050 Ti. Only the RX 570 gets about 50% higher frame rates, making it absolutely obliterate the competition in terms of performance. It's also possible to get the (full) RX 580 for around the same price as a 1060 3GB, despite the 580 performing at the same level as the full 1060 6GB card. I suspect there will likely be price drops for Nvidia's mid-range cards as well though, as we (hopefully) near their next generation of mid-range models.
I must say that I don't really get the point of the RX 580 2048 though, since it appears to be pretty much a rename of the RX 570. Perhaps they're just doing this to match Nvidia's naming scheme used for their 1060 3GB in that market, but you would think they would have done that long ago if that's their intention. Perhaps these cards have some other as-yet unknown changes, like being on 12nm though?