Dally and Darry are similar in that they are both leaders. Though their styles and leadership qualities are different, the greasers look to them both for guidance. Darry's physical strength and size as well as his inner strength are meaningful to the other boys, and because Darry is older than many of the boys, he takes on the role of a father figure.
Dally, on the other hand, has a dangerous history of being in urban gangs and living a life independently of others, so his ability to survive means he knows something about how to look after himself. It is Dally's self-reliance that intimidates other greasers and inspires them to admire him and listen to him when he has advice to give. These leadership qualities aren't as obvious as Darry's, but they still exert power over the other greasers despite their rugged appearance.
Dally gives the boys, especially Ponyboy and Johnny, advice and support when they are in trouble. He coaches them on how to survive, and he gives them very specific information about where to go and how to look inconspicuous. Dally also models quiet, hard strength for the boys, which means he gives them an example of how to rely on oneself.