Leonard should be remembered as the greater fighter.
Not only did he beat the better fighters, but he beat Duran twice. He also beat all of the other fabulous four fighters, something which Duran didn't do.
People will always give the excuse that Duran was a natural lightweight, though, despite him winning titles in the divisions he fought those fighters in.
Leonard was the lineal champion in three weight classes, while Duran was in two. If you're going by ABC titles, I would say it's relatively even. Duran won titles in four divisions and Leonard claims titles in five. But to be fair, Leonard won two separate division titles while fighting in one weight class.