The best overall device would be the Apple TV 4K, as its interface is the cleanest, and it receives new features and updates to Channels first. It also has ample storage, which allows for a decent live TV buffer.
If you do not wish to use Apple products, the Nvidia Shield is the best Android device. It is responsive, and has hardware/storage features on par with the Apple device. Also, its price is comparable, so it truly is the best comparison. However, its interface/menu is more cluttered if that makes a difference.
If price is your only concern, then your two best options are the TiVo Stream 4K, or an Amazon Fire TV Stick 4K. Both are roughly on par with one another, including their meager storage space, which equates to a minimal live TV buffer. Also, their interfaces are cluttered, with the Fire TV having the added "benefit" of Amazon ads constantly being shown.
The Apple and Nvidia devices fall within the $150–200 range; the other two less expensive devices are ~$50, but can frequently be found cheaper.
