We have several smart tv's in our house (adult kids have them in their rooms etc) and in my experience the Sony was the most buggy in regards to its operating system crashing and needing to be rebooted but did allow all apps.
Our LG has a nice operating system, updates regularly but has some limitations on the catch up tv apps for some channels, although they can be used on a web browser which is clunky. But the LG rarely if ever has operating system glitches.
The Samsung appears to be very good also. Does everything without glitches and seems to allow all apps.
All three tv's were in the middle of the range in regards to each manufacturers offerings, so not the most expensive but definitely one or two steps up from the cheapest for the size.
I do know that there are a lot of chingsing type brands on the market at a very reduced price but I do not know if they are any good or not sorry.
None of the tv's impress me much when it comes to mirroring devices or other computers to them. For the most part they are either clunky or too slow and laggy or have audio syncing issues. We generally use Apple TV for all that type of thing as it just works