first off, i doubt you're going to find any smart-tv models from the upper end brands (samsung, sony, lg) in a 50"for $500-600. at least new. that budget is tough to find even a non-smart tv from a majorbrand in of that size. possible with sales but still hard.
its a fairly low end brand (but better than dynex) but vizio's are typically fairly cheap for the options you get. it is a disposable tv though so if it breaks, there really arent replacement parts around to fix it like the top end brands carry. once the warranty is up if it breaks you're pretty much SOL. however, it does have alot of value if you dont have much of a budget yet want a large screen with options.
one thing to note: having smarttv functions is convenient yes but over time may lose support (as is currently happening on certain models) where the features stop working due to being out of date. some manufacturers provide updates but this is typically only for a certain period of time. the internet browsing feature is also typically quite limited.
a box like a roku (or similar type device) which has the functions you want will t ypically get far better longevity of support and is replaceable in case something new comes out with features you want more without getting too costly. they also typically support more apps and give you more choices.
just a few things to think about at least.