As has been partly discussed earlier in the topic, I think the biggest difference between new-school and old-school comics is the old-school emphasis on the personalities and moral character of the heroes in comics.
Whereas now, comics stories are more about sadistic power fantasies, intimidation, attitude and big explosions.

There's very little depth to the modern characters, and most of the characters are as depraved and self-indulgent as rock stars. (i.e., the heroes as portrayed now are not "innovative" and exploring new directions, they're just portrayed very inconsistently with who they were for decades until the writers of the last 10 to 15 years felt a need to use cheap tricks and shock elements, because they haven't the talent to write anything truly innovative. )

I was recently re-reading WORLDS FINEST 285 (November 1982):




Which aside from the great Miller/Giordano cover, has beautiful interior art by Rich Buckler and Sam DeLarosa, in a story that explores the friendship of Superman and Batman, and explores the heroism and self-sacrifice that makes them both such classically heroic characters, and a very compatible team.

Again, I miss that kind of heroism.