The difference is that the Dini-Hamill version is completely predictable. He goes through a set of formulaic, sometimes sadistic plots, and then gets defeated and then comes back, rinse and repeat. The new model as seen in the films and with Morrison (and to some extent, Nolan and Azzarello) is a spirit of chaos to go up against Batman's spirit of order. He has a permanent grin so that you never know what he's thinking. His speech is a wet rasp that only the insane can understand. Batman mentally damages himself trying to understand him, and he still can't do it; he one-ups a character who may or may not be the devil himself, merely for calling him a 'servant'. He's uncontrollable and wild and that is what, for me, makes him scary.
I will probably buy Tony Daniel's Batman. You will probably not. Now let's just electronically handshake and agree to disagree.