Giovinco never had the body balance needed to play for Juve. He's a great, talented player no doubt about it, but he just doesn't have what it takes to play for a top team.
Would love to see him play in La Liga, though.
Also, I'm not sure he had better dribbling skills than Dybala. Most of Dybala's dribbles are succesful, while Giovinco had the tendency to fall down whenever even slightly pushed by the opponent.
edit: Dybala would be among the top 5 attackers in La Liga if he played for Valencia, Atleti, Sevilla or Barca and Real.