In The Outsiders, why is it significant that Paul Holden is the Soc who steps forward to accept Darry's challenge?

Before the rumble begins, a handsome, athletic Soc named Paul Holden steps out from the group to challenge Darry, who represents the Greasers. Ponyboy mentions that Paul Holden used to be teammates with Darry, and the two boys were inseparable as teenagers. He goes on to say that Paul looks at Darry with contempt, pity, and hatred as he is sizing him up. Ponyboy then mentions that he could tell Darry hated Paul and was filled with jealousy because Paul had achieved everything he could not because of his difficult situation. Pony also knows that Darry feels ashamed to be representing the Greasers.
The face-off between Darry and Paul is significant because Paul Holden represents everything that Darry could have been. Paul is a privileged, athletic young man who had the opportunity to go to college, which is something Darry never had a chance to do once his parents died. Darry envies his former friend for being given the opportunity to play sports and attend college. Their face-off also underscores the class distinction between the two groups and differentiates Darry from the rest of the Greasers.

Paul Holden was Darry’s friend and football teammate back when they were in high school. It is significant that Paul Holden steps forward for Darry’s challenge because he not only shares a past with Darry, he is also the only Soc capable of going toe to toe with him. One can tell that Darry is (generally) feared by the Socs because he is well-built, athletic, and a good fighter.
The event also holds an important place in the story because it demonstrates the situation between the Socs and the Greasers. Before Darry was orphaned and forced to take responsibility for his siblings, he went to school and had a bright future ahead of him. However, his ambitions and aspirations are cut short by the accident that robbed him of his parents and his childhood.  On the other hand, Holden has not been around. He probably went to college and moved on with his life. Thus, their meeting only affirms the clear distinction between the two rival factions, in which one group is always at a loss.