Depends on the content - HDR 4K content on both Netflix and Amazon is encoded in horribly low bitrate - about 12-15Mbit/s which makes it barely look any better than 1080p content (for comparison - 4K BluRay discs are about 60-100Mbit/s and look infinitely better).
It looks better, but it's not even remotely close to how BR looks (and how 4K actually should look when bringing full resolution to the table) - even with H.265/VP9 it's quite bit starved at that bitrate.
