They all have really good pictures. Go to a store that has several brands and compare. Since they all seem to look great, you're mostly comparing features. What's important to you?

I've read that Vizio sells the most TV's. Samsung has to be right up there too. Costco has a lot of Vizio and Samsung models. Since Costco gives an additional year of warranty, they probably want to sell TV's that will last at least 2 years. They're pretty safe since all TV's ought to be good at least that long. They do get some back though.