Its not socialist. Socialist involves security for the poor. There is no security for the poor in china.I'll grant you that they're no longer communist, but they are socialist. Since the 1980s it's been in their constitution that they're a socialist nation. They've made a number of strides towards capitalism to make themselves more powerful on the international stage, yes, but they're still socialist. And their economy isn't "essentially" capitalist, it's socialist "with Chinese characteristics". It's half and half between government-owned services or production and an expanding open-market that's still so heavily regulated even Google can't compete with a government-funded service. Not even Wal-Mart has succeeded in China. It's not a capitalist market if the major international corporations in two different business sectors can't get a foothold. It's a socialist market.
You can also make the argument that it's authoritarian, but per the conventions of traditional authoritarianism their ruling party is too large to truly be authoritarian. Their single-party state is driven by a group of powerful men and not a single man who exerts influential pressure on the others who have any kind of power. Basically, modern China is less authoritarian than Stalinist Russia, so that should tell you something.
Plus, China refers to itself as "a socialist state" per its 1982 constitution, and uses that term to describe Marxist-Leninist communism just like in the USSR. So you can argue that the Western's definition of communism and their definition of socialism aren't good for deciding which of the two they are, but it's either heavily-refined communism or socialism. Authoritarianism isn't really on the menu