Kind of unfair to compare Didi (or any Chinese company) with the free market alternatives. If you're given state sponsorship from one of the largest countries, then you should easily be able to do more rides than Uber.
It was apparent that Didi had achieved the network effects necessary to overcome Uber in volume. Both companies wanted to focus on revenue so it was savvy of Didi to purchase UberChina so they could reduce ride subsidies.
I think that the success of UberChina, along with Yum! and Wal-Mart, demonstrate that it is possible to prevail in the difficult Chinese market.
What were the differences?
It was used as an example to illustrate that Didi did the little things that remove friction for its customers. Didi also recruited drivers in smaller cities; its coverage was superior to UberChina's.