In some ways it depends on your perspective, but if you look at it in terms of who ends up as the "winner," I would lean towards pointing to Jack as the most "effective."
Ralph is described as a boy who yearned to be a leader, who longed to be important and seized his chance as the boys are gathering after this plane crash on the island. He tries very hard to act as an adult and set up rules and procedures that will help hold them together.
Jack immediately assesses the needs that the boys have as well as their wants and quickly starts to pull boys away from Ralph's rules and structures because he understands their need to band together against their fear, their need to give in to their hunger and the power that he can have over them as the master of the hunt.
So in the end, Jack draws away almost all of the boys because he is able to understand more clearly their wants and needs whereas Ralph is a bit too concerned with making things work the way he thinks they ought to.