For a small to medium displays at typical viewing distances (this includes most "big screen" panels you can buy at your local electronics shop), 1080p meets or exceeds the limits of the typical human eye's resolving power. Without using a projection system and a large screen or a stupendously expensive (>100" diagonal) flat-panel, 4K is a subtle upgrade at best.
When video is encoded with insufficient bandwidth, compression artifacts (e.g. macroblocking) are anything but subtle. These artifacts typically are not constrained to one or two pixels, but ramify to much larger portions of the image. Netflix has, by necessity, used insufficient bandwidth on practically their entire library. My money is on Netflix's over-compressed 4K being inferior in quality to Bluray 1080p for the vast majority of users.
When video is encoded with insufficient bandwidth, compression artifacts (e.g. macroblocking) are anything but subtle. These artifacts typically are not constrained to one or two pixels, but ramify to much larger portions of the image. Netflix has, by necessity, used insufficient bandwidth on practically their entire library. My money is on Netflix's over-compressed 4K being inferior in quality to Bluray 1080p for the vast majority of users.