i think Batman fights his demons first of all and as a side effect he fights villains. also i dont think he is a true superhero, i think he is a man in superhero costume. what is his intrinsic superhero power , maybe i miss something ? on the other hand, joker doesnt have any fancy costumes or tools, just his insanity. but its hard to relate to joker either - he is a messenger of death. you see this is a problem with "Batman universe"  - no true protagonist , real hero - we don't choose between the good and the bad, but between a  troubled and complex in his motivation man and villains. this is more realistic obv, but is this a real superhero film though? answering your question -  I don't relate to neither of two. I can empathize more with Joker for sure, although I know that he needs to be defeated.