To add to what @djcastaldo said, if you're going to use ethernet for the Apple TV, the Apple TV 4K's ethernet is much faster. This leads to way better seek times.
Because the original Apple TV 4th generation uses a 100mbit ethernet, it leads to slower seek times than if it was on WiFi. That's only if your wifi is faster than 100mbit of course.
The problem with the Apple TV 4th gen is that it puts you into the predicament of getting better seek times by being on wifi, which most people in the community will agree, is less desirable than ethernet. Using wifi means that it sucks up a lot of bandwidth while watching TV, leaving not as much available for other devices. It's reliability can also be effected by other devices on the wifi. And mostly, people just don't trust wifi over a wire