I would opt, if there's still room for a decision, for the external streamer as well. Case in point: I bought a brand new Vizio 50" 4K TV that advertised lots of apps and the ability to add more apps if the ones you want aren't pre-installed. That actually turns out to be quite misleading since the ability to "add apps" is limited to ONLY the list of apps that ships with the TV. And in my case Vizio has never supported putting Sling TV on most of their TV's and that's the app I want to add. Screwed by the "smart TV" that aint so smart.
It wasn't a real loss because I have ROKU boxes in the house which have worked quite nicely. I chose in this case to put in the newest version Apple TV. I made that decision, despite the cost, because I have an entire Apple ecosystem here and it gave me a function I couldn't get with the ROKU. If you aren't hip deep in Apple stuff, you'll be better served with a ROKU
click here, or Nvidia, or any of the plethora of little streaming boxes.
The TV is the least flexible place to get your apps. But, if what you want is already there, it really won't hurt you much. I have one TV with all the apps pre-installed and it gets by OK.