|What differentiates the Roku and other boxes and what they offer from the streaming TV packages is a single interface (channel) for viewing all cable channels as well as local TV, all live, like a DVR connected to cable or satellite. The only difference is the signal comes over the internet and not the cable or satellite dish.|
The Roku may offer PS Vue, DirecTV Now, YouTube TV or other streaming packages as a channel you can access. That's how it works on the Apple TV 4 and 4K, you can install any channel you want, including the streaming channels.
I know the Roku was the best box to own for years if you wanted access to the widest variety of channels, especially when Amazon Prime Video was not available on the Apple TV. It finally is, but my guess is Roku still has access to the most.