Vietto gives me the impression, that he can be adjusted easily for a top team than Dybala. He suits perfect in European football althought this is his 1st year.
Also, he has an experience from European league (EL) and he scores more for his team.
I'm sure he will be a world class player while i'm scared of Dybala because he can be an ''Iturbe case''.
Don't forget the price. Surely Dybala is much expensive and difficult to negotiate with Zamparini.