Roku 4 vs. Amazon Fire TV reviews: Which box is best for 4K streaming?

First came the 4K TVs, now come the 4K streaming boxes. Roku and Amazon both launched 4K media streamers last year, letting users watch higher-resolution video without having to rely on the often-clunky interface of a smart TV. But aside from their ability to play Ultra HD content, the Roku 4 and second-gen Amazon Fire TV have