The Corleone Family would be less powerful, because Freddo cannot make the people respect him, remember Moe Green hit Freddo`s face.Freddo is not as clever as Michael and he doesn`t work seriously.That`s why Vito decided to make Michael the Don instead of Freddo, but to tell you the truth, I think Vito knew Freddo was a pontential traitor to betray the family in the future. Remember Vito was a man who lives the future before it cames.