GMD and CCP are usually much more common. KMT is generally almost only exclusively used to refer to the party as it exists in Taiwan at the moment, though this is a somewhat recent change. I've actually never read a historian that uses CPC instead of CCP, poli sci people are somewhat different however.
CPC is a relatively more modern standardization as far as I know. My suspicion is CCP is used because it is a more literal translation of the original Chinese. I wouldn't attribute much else to that choice.
GMD and CCP are usually much more common. KMT is generally almost only exclusively used to refer to the party as it exists in Taiwan at the moment, though this is a somewhat recent change. I've actually never read a historian that uses CPC instead of CCP, poli sci people are somewhat different however.
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CPC is a relatively more modern standardization as far as I know. My suspicion is CCP is used because it is a more literal translation of the original Chinese. I wouldn't attribute much else to that choice.