Well, to be pedantic, this is not "4k" either, as "4k" is a long-standing cinematic term which describes a slightly higher resolution than "Quad HD" aka "UHD". For 4k FILMS, typically they are shot in "real 4k", which is to say 4096x2160 (4096 wide is why they are called "4k" in fact), not in "QuadHD" or "UHD", which is to say 3840x2160. If that bothers you, realize that most films projected in 4k were actually done in 2k, until very very recently. And 2k is just a smidgen wider than 1080p resolution in exactly the same way as 4k is a smidgen wider than UHD. More importantly, for FILMS as you say, the very very important bit of the UHD standard which Amazon does not appear to be supporting (likely for lack of bandwidth on their HDMI 1.4 port, but that is conjecture) is HDR. High dynamic range is what allows a dark scene of a FILM to look great in a theater, yet devolve into a puddle of gray-brown mud on a typical screen. HDR is an optional part of the UHD standard, in non-4k resolutions as well as in 4k resolutions (a part that those "cheap" 4k TVs tend to not actually support, which is why they are cheap). Given the very real bandwidth constraints both on the Internet connection coming in and on the HDMI 1.4 connector both boxes are using, I'd be much more excited for FILMS to see HDR supported on a 1080p stream than to see mud rendered with absolute pixel perfection on a 2160p stream.