Jack uses his power to gain more power for himself. He seeks to build up his power so everyone follows and obeys him - so everyone does his bidding, and he becomes essentially a dictator. The reason Jack desires power is to make himself feel more powerful.
Ralph uses power for the good of the group. He wants people to listen to him because he believes he offers the best solution for the group as a whole. He is more interested in creating a functional "society" than amassing power for his own well-being. The problem is that Ralph does not possess the charisma that Jack does. Jack has more drive because of his personal goal of power.