I think that Sonny was more old-fashioned, more traditional. He would've been more like Vito in the ways described here. But, remember, Sonny did not have his father's intelligence. He allowed his hot head to rule his actions, something that would prove fatal.

Please remember that Fredo, Sonny and Connie never ventured outside their little world. We would have to assume that the Corleones did not have much contact outside of that close-knit Italian community. The three siblings never went to college. They never experienced the world outside of their own; it was very insular. The boys went to work for their father and Connie was home with her mother. the only exceptions were Tom, who obviously went to law school, and Michael, who was in the service and then college.

Because of their exposure to other cultures and lifestyles, Michael and Tom were the only ones capable of bringing the family in a different direction.