From Fangraphs in December (although I can't find this on the site somehow):
"Arias looks like a typical top-of-the-class shortstop. His skill foundation (high-probability shortstop, viable hit tool from both sides supported by in-game performance) combined with his body projection creates lots of positive potential outcomes, the best of which would be Arias' maturation into the Goldilocks Zone, where he'll have added strength via maturity to hit for power, while also staying agile enough to play shortstop. That's the type of outcome that would yield a star player. If an aspect of his offensive profile falls short, the possibility of him either hitting or hitting for power while staying at shortstop would mean Arias becomes merely a solid big leaguer. Arias shares body and swing similarities with Cleveland shortstop Bryan Rocchio (the Rocchio of right now, not Rocchio when he was Arias' age), rolling his hands and elbow through contact in a way that enables airborne contact to all fields. There are hit/approach elements the industry can't be sure about until it sees Arias face pro-level pitching for an extended stretch, but he's been considered at or among the top players in his class for a few years after performing in a showcase setting."
Rocchio is 21 and their #58 MLB prospect overall, it is crazy they are equating the two as far as hitting currently. I get the sense that Arias right now is ahead of both Dominguez (a CF) and Alex Vargas (who Fangraphs still has as their #67 overall prospect even though NY never promoted him to low A last year).