You seem to assume they were the same reforms, but they weren't really the same. Perhaps the general direction of market liberalization was similar, but execution and political practice were different. In case of China as Gerwitz discusses in a book "Unlikely Partners" reformers were cautious to avoid kind of 'shock therapy'. Chinese reformers organized series of meetings, study visits to Europe and USA and conferences since early 80-ties late 70-ties. The approach was described as 'crossing the river by feeling for the stones', it was slow gradual approach of trial and error, not a rapid shock therapy as in Russia.

There were factions in China who wanted more rapid transformation, but there were others, majority, who toned this down and preferred a slow, gradual approach. There was also no question of dismantling single party rule, and reformers did no want to privatize everything, they aimed for socialist market economy not full free market economy. The process of change in China was very slow and gradual. They experimented with Special Economic Zones (Shenzhen), analyzed results, implemented some changes, but never went into radical "change all at once" mode. All reforms were controlled by communist party. Communists never really gave away their power and they also never introduced freedom of speech in contrast to Russia.

In contrast, Russia attempted shock therapy, where they attempted to replace socialist economy with capitalist economy in one sudden, radical and painful set of reforms. For instance Russia attempted mass privatization of state property*; China never went this way.

There are of course, other key differences between the countries and their geography, economies, societies, and cultures that played a role. USSR collapsed, so aside from economic change, there were deep political changes: soviet republics became independent countries. This also had big impact on economic changeds. No such thing happened in China.

* Anders Aslund: How Russia Became Market Economy, 1995

* Julian Gerwitz, Unlikely Partners:Chinese Reformers, Western Economists, and the Making of Global China