Piggy would be the best leader because he knows more than the other boys.
He is more smarter in what is needed than the others. "We got a lot of stick" We could have a sundial each". (Pg.54)
Piggy is more reliable than the others. "I know I cant see very much, said Piggy, but have we got any smoke?" (Pg.55)
Piggy is more mature than the others. "Piggy discounted all this learnedly as a mirage." (Pg.48)
I know some people may think that because Piggy isn't popular or because he is fat and has Asthma would make him a horrible leader.
Piggy may be fat, have Asthma, and be unpopular but that doesn't stop him from being more mature and smarter than the "cool kids" not to mention he was right about how they were doing things the wrong way in the beginning. In conclusion, Piggy would make a more knowledgeable leader than the other boys.