Which do you think? Perhaps both? We know he couldn't break Jade Maiden until he read 9 Ying, which suggests that he did improve in the external arts. However, there doesn't seem to be any evidence to show that 9 Ying was internally any better than Xian Tian Gong. Obviously, there are parts of internal 9 Ying that is better than XTG, such as being able to recover damaged internal in months instead of years. However, could Xian Tian Gong be equal to 9 Ying in internal cultivation alone?