There are lots of things you need to know before buying a smart TV & the OS on your smart TV will define its interface and software capabilities
That’s like asking ‘what’s the best nut to get kicked in?’
The dumbest one
I own Philips TV with their own OS which is semi-smart and kinda sucks. I hooked it up to Xiaomi Mi Box and enjoy Android on it.
I just plug my laptop into the TV. Works and looks great.
None. Any “smart” TV won’t be upgradable. It might get a few software updates but it will eventually be incapable of being updated enough to function as it used to with changes in services and codecs.
I have Roku and Fire devices, even on the “smart” TV. When the device isn’t enough anymore I can just replace the device for like 20 bucks, not so for the built-in software on the TV.