Ralph is a natural born leader, but Piggy isn't. Ralph successfully rallies many of the boys into following his plans for survival, until they revolt. Ralph proposes two primary goals -- survival and maintaining a beach fire to notify passing ships of their location on the island. Piggy is young, overweight and wears glasses, so the other boys tease him and show him disrespect. However, Piggy is the brains behind most of Ralph's plans. For example, Piggy comes up with the idea to use a conch as a signal, so all the boys can unite in one area. The conch also becomes an important symbol of leadership and authority.
Piggy relies on rules, order and morality to govern the group of marooned boys. Ralph agrees with Piggy's values and appreciates his intellect, but he's more likely to rely on instinct. Ralph doesn't trust that the disgruntled group of boys will always make rational, logical decisions. Both Ralph and Piggy are idealistic and believe they will be rescued, but Piggy falsely believes that negotiating tactics, fairness and reason will win over the boys who've gone rogue.
Even though Ralph appears to be more confident and self-assured than Piggy, Ralph desperately wants to be liked, appreciated and respected by others in the group. Ralph is obsessed with popularity. As a result, he often picks on Piggy to make himself feel important, especially when the older choirboys question his leadership or test his abilities. Piggy relies on science to govern his behavior. He believes that democracy, justice and equality will prevail, and doesn't care whether he's popular or not. Piggy's self-esteem is rooted in his intellect and deep-rooted value system, not his rapport with the other boys.
Leadership weighs heavy on Ralph's shoulders, and he undergoes a serious emotional blow when the boys accidentally kill one of their friends. He nearly loses his ability to react sensibly when one of the choirboys, Jack, undermines his authority. Piggy maintains a level head throughout the novel, and doesn't allow his emotions or his feelings to interfere with his decisions. He approaches obstacles pragmatically, and unlike Ralph, is always aware of the bigger picture. Golding uses Ralph to represent the childlike, emotional response humans often have to troubling situations, whereas Piggy symbolizes the analytical, objective, adult-like side.