intothevoid
Super Freak
My explanation is that the Joker with make up on Looks strange and cartoony looking, this is why the DX head looks stupid IMO.
Thus, it is hard to see the actor underneath the make up easy. So basically what you are seeing is an illusion and if you try to create the strange looking character your seeing, you will not be able to capture the actor that makes the whole package come together.
You will be only be creating an image that you only see with make up but unable to capture the whole process that makes the character come together to look like the actor as well as the character.
I can see how someone could do an incredible Ledger Joker sculpt using both methods.
I know Adam uses the Actor first - Character later method and it works for him. I don't know for sure how HT do it but if they are indeed straight sculpting Joker then maybe that explains why they miss certain aspects of the likeness which the Adam sculpts capture very well.