I think this might be one of his weak spots, when he's been asked about the carbon tax issue previously he starts to talk a little too much like a microeconomist. When he was asked about this by Rosemary Barton he went on for too long and it became convoluted. The public won't get a lot out of his explanations unless they get a lot simpler and until then the conservatives can say basically what you just said: his new system will deliver largely the same outcome.