I think that glint of triumph in Dumbledore's eyes means that Voldemort only has one option to him now if he wants to save himself from certain death. He must feel remorse. And knowing Voldemort won't ever feel remorse for the things he has done gives Harry that edge. I think it deals much more with the horcruxes than we originally thought. To put your soul back together, you must feel remorse. And to save yourself, you must feel remorse. So Harry has a distinct advantage here, because he can feel remorse.