I don't recall who, but somebody pointed out a few months ago that Caroline has the most room to improve because she has the most problems. ( How is that for ironic? ) The more problems she fixes, the better she will get.
While I am not an uber-fan of either, I must concede that Mao and Yu-Na are great athletes - the best in the world. There will never be a competition where somebody hangs a gold medal around Caroline's neck while Mao and Yu-Na get less, or nothing.
( Wait a second. That happened this morning. )