Abolishing the NEP in the USSR and moving onto more planned economy ended up being beneficial. However, in the case of China, the NEP-inspired socialist market economy is the reason China is where they are today. New contradictions have arisen, which is of course a gamble, but with that came highly developed productive forces and tight interconnection with the global economy. This has allowed the PRC to reach where the USSR could not, and the developed productive forces are forming the basis of the newly emerging, more planned economy.
As for Mao, China was horribly underdeveloped. Many of his mistakes were in dealing with such an environment, knowledge of agronomics was low and industrialization was non-existent. Under Mao, a solid socialist base was laid out, which managed to created the basis for the modern economy.
As for the Sino-Soviet split, it's a tragedy, and was avoidable.