Sorry folks, but talk of using PC monitors and external Freeview boxes just to watch a bit of telly in the kitchen really is a complete load of nonsense. These are bachelor / nerd solutions. They're okay for someone a bit techie who lives alone, but not really for people whose partners just want an easy life. Keep it simple; go for a 28" or a 32" TV with a HD tuner and an aerial feed. That's job done for the Missus.
For smart features, really, go for whatever works. If that's an ATV because that matches content already owned, then sure. You've a better chance with that than anything the TV manufacturers can cobble up.
The TV manufacturers never really got to grips with integrating a decent set of smart features. Partly this is to do with their distinctly 20th Century mindset. They're still focussed on hardware solutions. They never worked out how to make money from content in the way that Netflix, Amazon, Apple and Now TV (Sky) has, and nor did they form the sort of strategic alliances with the smarter players in the market to co-opt or leverage their tech. Sony really should have had the best shout at doing this. Of all of the big electronics brands, they're the ones with film, TV and music production arms; but it wasn't to be. As a result, the TV makers are constantly behind the curve. Their platforms are designed around the idea of corralling the user experience within a tightly-controlled suite of hobbled apps that they have insufficient funding to support beyond a couple of years from launch. IOW, Netflix, iPlayer, Youtube and the rest on a smart TV may look like the versions you on your phone or tablet or other smart-enabled devices, but they're really just a version or interpretation of the basic framework, and although built from some of the same core ingredients, there are enough differences that make them a virtual cul-de-sac.
The crucial differences with 3rd party devices are that the hardware is designed with some longer-term degree of software support in mind, and the companies behind ATV, Amazon Firestick, Now TV, and the rest have deeper pockets.