Yeah he's mostly Sonny for sure. He changed so rapidly from the beginning to the end though that I can see why he said he was like Michael as well because in the end he was more refined. But also I can sort of see the Vito tie-in too since when Vito started out he was nothing more then a rough steet thug who had to prove himself through aggressive violence etc. and that is what Vincent was like when he first came into the scene.