I have samsung smart tv and a tcl smart tv at home both roughly of same age.
I personally feel there is only a negligible difference in picture quality between both. But the real difference is evident when it comes to sound quality and processing speed.
The samsung sound quality is superb with clear vocals and a good bass, it switches between apps like a breeze and never crashes any app or freezes.
The TCL on the other hand sounds like a China speaker, slow processor speed, app crashes, random errors etc. But does the job if you are patient enough.
The difference in price speaks for itself.