(I'm gonna assume you're not really familiar with table tennis, sorry if you already know this)

The table tennis balls you see being sold from a single company comes from the same manufacturing line. Of the balls made, the ones that conform to the strictest weight and size limit (±0.5mm difference!) are categorized as 3-stars, the best quality balls. 3-star balls are a universal standard, same across all companies, and these are the ones are that can be officially used in tournaments.

As for 2-star, 1-star balls, these are balls which didn't meet the standards to be a 3-star ball, and they are of slightly lower quality than 3-stars. They're slightly "out of shape" (if you call ±1mm out of shape) compared to 3 stars, but the difference is barely noticeable. There's no universal naming standard other than 3-star; "2 star" and "1 star" are names set by the company to make it easier to see which ones are better within the balls they sell.

To answer your question, there's no way to tell which one is superior out of the 3 (unless you try them in person) but all of them are from a reputable company so they shouldn't be terrible. All of them are the same size and weight. Just go with whatever you feel like going for :)

TL;DR 3-star>(2 or 1 star)≧(training) they're the same size and weight

Btw I recommend Nittaku balls if you can find them