Ralph and Jack both offer very different qualities and styles of leadership.
When Ralph first summons the boys with the conch shell, he becomes the obvious choice for chief of their fledgling tribe. Ralph had a "stillness" that "marked him out: there was his size, and attractive appearance; and most obscurely; yet most powerfully, there was the conch" (22). Ralph has the "directness of genuine leadership" and attempts to be fair to all the boys and look after the littluns (25). Ralph instills rules and order on the island, but struggles with maintaining the discipline to enforce the rules.
Jack, on the other hand, is "the most obvious leader," since he already has experience leading the choir boys from his experience as "chapter chorister" and "head boy" (22). The choir boys vote for Jack out of obligation, but do not seem very enthusiastic; their response indicates that his style of leadership was less than favorable. As the novel progresses, Jack gains power as the new leader of the hunters. They respect him for his stregth, lack of fear and ability to kill. His leadership style is based on intimidation and fear, using terror to command and dominate the younger boys, like Sam and Eric.