Dr. Hahn is a professor of Scripture at Franciscan University of Steubenville. Steubenville is one of the few Catholic schools on this continent where the entire theology faculty takes an oath to be obedient to the Roman magisterium. If Dr. Hahn were heterodox in any significant way, he's already on record saying he's bound to obey the order to change his teachings.
Bob Sungenis is a lay apologist. He runs his own apologetics apostolate, responsible to nobody but himself. The fact that he calls it "Catholic Apologetics International" does not prove anything about its orthodoxy or reliability.
Going to Bob Sungenis to trash Scott Hahn mostly just proves that some people disagree with Scott Hahn. But we all already knew that.
Robert Sungenis is working on his doctorate in theology. Simply because he has a different apostolate from Scott does not make him any less qualified.