(Excuse my English, not my first language)Until Stalin's death in 1953, USSR's ideology was Marxism-Leninism, an authoritarian form of communism based on Lenin's theories. Russia being an agricultural society, they focused on industrialization, especially in heavy industries (necessary according to Marx to achieve socialism and useful if a war was to happen to protect the country). Their attempt to collectivize agriculture was a failure and brought a lot of oppositions from the peasants. They also tried to modernize the country's infrastructures with a vast politic of public work (mostly ineffective). The agricultural society had to disappear to allow for a new urban, industrial society to rise. However, as popular distrust in the government grew, in 1955 Khrushchev publicly acknowledged Stalin's "failures" and went on another path, with a lighter form of interventionism. This is where the difference with China is. China still followed a marxist leninist doctrine, adapted as Maoism. It focused far more on the peasants and the agricultural society that was prevalent in China and collectivization of the lands worked far better. Since a lot of opposition to Mao came from town "intellectuals", Mao emphasized on farming even more, and the intellectual elite became one of his biggest target, a lot more than in Russia.Also, instead of sending political opponent to forced labor (aka gulag), Maoists believed in self-criticism. The "enemy of the people" were to be re-educated in camps, where they were publicly shamed and conditioned to accept Mao's doctrine as an indisputable truth, with no use of physical torture necessary.

It is also worth mentioning what China is doing now, and how that arose. Officially, if you ask them, the government of China is still as Communist as ever. However, they will openly admit to moving away from the ways of other well-known communist countries (e.g., Soviet ideology), because China has, as it were, made Communism her own, adopting a form of communism with "Chinese characteristics".

What this actually means in practice (though it would be inadvisable to say so in China) is that after Mao died, politicians with a bit more sense (and perhaps also more concern for the well being of their own country) came into power and began actively -- but gradually -- moving away from many of Mao's worse ideas and in fact away from what we in the West would define as Communism, strictly speaking. They haven't entirely finished moving away from Communism yet (the state-owned sector is still very large), but they have made very substantial moves toward capitalism in particular. (Note however that moving toward capitalism is not at all the same thing as moving toward a Western-style representative government.)

They have invented phrases like "market Communism" to avoid outright admitting in public that Mao was wrong, because he is greatly revered now by the Chinese populace, in much the same way that nobody in the US criticizes Lincoln, regardless of their political leanings. But the government itself has effectively realized that Mao was wrong about many things and has developed a carefully unstated policy of moving away from his economic principles, gradually and in a controlled fashion, so that China can prosper.

There is an entire chapter on this in Greenspan's book, Adventures in a New World.

Have the Chinese or Russians ever said the spiritual fathers of communism were wrong for thinking the whole thing should be democratic?