It's subtle. But it looks as if the Large is more of a Superman S. The 28-S is a good coin anyway. Do they know how many Large S's were produced?
1 out of every 25 1928-S is a large S variety. From a study done by Jack H. Tod Info from "A Complete guide to Lincoln Cents" by David W. Lange. If my math is right that comes out to 4% are Large date.