Google TV is a smart TV platform and comparing the LG HDTV with Google TV to an LG HDTV running a different smart TV platform is simple. The Google TV version will run Android 4.2.2 and run various Google apps from Google Play Store, those designed for Google TV specifically. Both are going to run many of the same internet streaming services such as Netflix, Vudu and YouTube. In general I would consider Google TV more difficult to use but capable of much more, primarily as a result of Play Store access and the Chrome web browser. I use Google TV often and the only other smart TV platform I have used often is Roku, both are awesome and important for me having cut the cord years ago. I would say the non Google LG smart TV platform would rank considerably below Google TV and Roku, at least for what I want from a smart TV platform.
Other TV makers of course have smart TV models and the capabilities vary greatly. I would say buy Google TV if you don't mind requiring greater effort to use your smart TV, the results are worth the effort.