I own one. I like it, but I cant comment on it’s 4K Capability yet since I don’t have a 4K TV. And since the 4K Apple TV isn’t yet in my hands, I also can’t comment as to what is better since I haven’t tested them both.You can do it on the nVidia Shield. I have one. It supports Atmos too. And you can stream games on it (from nVidia or from your PC). Apart from the cheaper 4k titles, it's much, much better than this new Apple TV, and it has been around for a while.
I also have a shield tablet, and once had their Shield handheld portable Android powered game device before it was taken over by a relative. Still love the tablet and use it from time to time to watch Netflix, or play some of my casual supported PC games.
Great devices though!