Final answer:
Without specific details from Millar or Polybius, we base our comparison on the complex governmental structure of the Roman Republic. Likely, both authors would describe its centralized and distributed elements, given the roles of assemblies, consuls, senate, and the influence of powerful families.
Step-by-step explanation:
How Millar's description of the Roman government compares to Polybius' is not explicitly detailed in the provided text.
However, using the information given on the Roman Republic's complex government system, which included the Centuriate Assembly, consuls, senate, and ties to the priesthood, and noting the system's longevity and adaptation as Rome grew into a global power with various government levels, we can deduce some general information to address the question.
It is likely that both Millar and Polybius would highlight the checks and balances system, such as the consuls' authority being limited by short terms and mutual oversight, the senate's control over state finances, and the intricate patron-client relationships that influenced political decisions.
Given the complexities of the Roman Republic's government, with its multiple assemblies and layers of administration, both authors would probably describe it as a blend of centralized and distributed authority - centralized in certain aspects but with significant power spread across different groups and classes.