Old School versus New School RPGs

A very perceptive quote on the difference:

Old School is about saying smart things, New School is about rolling hot dice. They cannot get any more different than that. In Old School you succeed or fail based on your ability to make clever inferences about the game world and/or say things which count as clever within the context of that world. But it's basically a test of the cleverness of the player. New School, on the other hand, is a test to see whether you can roll high. If you roll high, you win. Those are very different games.