As an allegory, "Lord of the Flies" has characters who stand for qualities beyond themselves. As such, Ralph represents the "golden boy," the born leader who has the charisma to move people. When the boys first arrive on the island, Ralph removes his shirt and happily baptizes himself in the water,
He turned over, holding his nose, and a golden light danced and shattered over his face. Piggy was looking determined and began to take off his shorts. Presently he was palely and fatly naked.
When Ralph says that his father will rescue them, Piggy asks,"How does he know we're here?" Ralph thinks only "Because....because....because." Later in the novel as Ralph hides from the hunters, he realizes his shortcoming, wishing he could "think as Piggy can."
Piggy, thin of hair, fat, near-sighted, represents the mature adult who uses reason to solve problems. For this reason, he is superior in leadership to Ralph; however, because he does not make the "golden" appearance that Ralph does, Piggy cannot get the respect of the boys that he needs in order to lead.
In Chapter Nine, although his hunger makes him weak enough to join Ralph in meeting with the hunters so that they can have some meat, Piggy is wise enough to assess situations; when Jack exploits his power, Piggy urges Ralph,
'Come away. There's going to be trouble. And we've had our meat.'
Unfortunately, Ralph does not listen and they are trapped behind the "fence" of brown bodies that shout "Kill the beast....cut his throat" as little Simon gets swept into the circle after Roger has left, having pretended to be a pig. Since the boys have so worked themselves into a frenzy of blood lust, Simon falls victim, proving Piggy's words of caution all too true.
Glasses, obesity, laziness and "ass-mar" aside, Piggy is by far the most intelligent character among the castaways of William Golding's Lord of the Flies. Ralph realizes just how much he misses Piggy shortly before the latter's death, and during his flight from Jack and his hunters, Ralph often asks himself what Piggy would suggest. It is Piggy who understands best the power of the conch (a symbol of free speech, among other things). With or without his glasses, he sees Jack as a danger to the tranquility of the island and the depths of his hatred of Ralph. He is the first to suggest moving the fire from the mountain to the beach to avoid the beast.
Jack has a simple way of dealing with opponents: He either kills them or forces them into joining his band. He uses the "might is right" approach to subdue his opposition, and his physical stature as the biggest of the children is also utilized.
Jack convinces the boys that they have killed the beast and not Simon, telling them that it must have disguised itself.
I would say that, in this chapter, you can argue that Piggy shows that he is more perceptive than Ralph is. This may be because Ralph is too concerned with keeping power and with being the chief.
We can see this is the scene where Jack is challenging Ralph's authority. Piggy tries to prompt Ralph to talk about rescue and the fire -- things that are good reasons not to obey the hunters. But Ralph wants to just insist that he is chief and that everyone must listen to him just based on that.
Piggy then tries to get him to leave because there is going to be trouble. In these ways, Piggy is more insightful and wiser than Ralph.