Any question like this will feature different answers. In true Stargirl manner, one should try to embrace as many of them as possible. I think that one of the most powerful lessons from Spinelli's work is that time moves fast. In order to make the best of it, one might have to break from the pack and find their own path. Those that do, like Stargirl, might live a more contented life and impact those who will follow them. Stargirl might not have set out to make the world a better place, but because of her spirit and her willingness to embrace her own identity in a world of conformity, she is able to do just that. Leo, on the other hand, is plagued with the hypothetical because he was imprisoned by his own fear. I think that Spinelli does an excellent job of showing how social acceptance and the seemingly pressing need to conform are temporary conditions. They are reflective of a contingent moment. The only transcendent condition is the character and sense of dignity that one has within them. In order to overcome this painful state of contingency, one has to revert to their own sense of identity, the element that stays with them for the rest of their lives. It is for this reason that Stargirl is happier and leaves an impact back on MAHS. It is also for this reason that Leo ends up being a character shrouded in what could have been as opposed to reveling in who he is, as Stargirl does.