And NY, I’m convinced it should be “younger appearance than today.” But I’ll wait for the grammar cops to make that decision.
The Grammar PO-liceperson says that the sentence could be rewritten. For example, “Dr. Hahn and Mr. Cavins looked younger in 1996 than they look today.” The original phrasing was comparing grammatical apples to syntactical oranges, as it were; therefore, neither “different from” nor “younger than” really fits correctly into the sentence structure.
Oh, ouch. More coffee.
Thank you for the astute observation and correction. The original sentence was composed in a rush. The one rule I try never to break is that of ending a sentence with a preposition. Thank you, again.