When I looked for TV last time, I can't find the one that I like that is not smart TV. So, I just bought one. Actually I was looking for just TV too. On my second thought; well, if I have smart TV, I can just switch on TV without bothering about the android box HTPC or whatever external unit. I can find one box later for more feature.

Having external one is good since the built-in one in the TV will be outdated fast. They probably update GUI and put more function. Later the unit become low on RAM/ROM and performance become sluggish. Most likely after 2 years no more upgrade and no more being bothered since new TV models come out each year nowadays

Any external box is the best choice. Can easily replaced since they are outdated fast too. For longer stability and more flexibility, I'd go for a small PC like NUC and I'm still looking for one after a year. Waiting for better one or price going down, but every time you see new model with better feature and new price and keep waiting and waiting Anyway, I'm in no rush because my TV is already smart TV

Yes, buy separate external box

Just buy the TV you like within your budget. If the one you like is a smart TV, just don't bother about price difference. That was what I did