For movies, use Movies Anywhere to access your library from other services. There is no solution yet for TV shows.For me it’s really just for iTunes since I buy so much of my stuff on there. If it wasn’t for that, I probably wouldn’t care too much about Apple TV. Someone please tell me I can get iTunes stuff on smart TVs now. PLEASE
I think a lot of the long term value in streaming boxes comes from the length of time you own a TV. Even if your TVs smart functions were great when you bought it, how long s o you think it will hold up before performance lags, or new services are unavailable.
Do you expect the hot new new streaming service launching in 2020 to run well, if it at all, on your high end smart TV from 2015?
Tech is constant march forward and having the UI separate from Display can greatly extend the life of the display.
Honestly I feel like this conversation can only happen at the launch of a new spec like HDR/4k since this forum is a self selected group of people who have very recently bought new TVs. However we are not representative of the market at large.
I think most people here going the smart tv route today, will be happy to have streaming devices on the market in a few years to give that TV investment a shot in the arm.