I have both. The smart TV functions, to be frank, are absolutely terrible. Netflix takes 2-3 minutes to load on my TV, versus 5-10 seconds on Apple TV. Plus, my Apple TV works with all my Apple devices, which my TV does not.
I have both and the smart functions on my tv suck. It's super slow and clunky. One day I was trying to use it and it locked up. I couldn't do a thing on my tv. It wouldn't even let me turn it off. I had to sleep all day with the tv on until my mom go off of work to unplug it for me. That was the last day I ever used the smart functions. It just isn't useable for me because of my physical disability. I need my tech to work. And when it doesn't work I need to be able to fix it myself. When the tv goes wonky I can just restart it via the settings.