There are many differences between Dean and Sal clearly. The main one that stands out to me though is that it seems that Dean is running away from something while Sal is in search for salvation. This is clear in the book when Dean goes crazy and just starts talking about all the places he wants to go and all the girls that he wants to be with. He is most indecisive with his choice of girls. It seems that everyone that he meets, he wants to marry. Sal looks up to Dean as a roll model so Sal will basically just go with the flow with whatever Dean does. As a character, I think Dean is a bad influence on Sal.