Neither centralization nor decentralization have anything to do with corruption or the lack thereof. The pros and cons of a centralized state have more to do with state strength and its capacity to enforce policies, regardless of how harmful or corrupt these policies are. USA might be considered a decentralized state, theoretically speaking, with the endless checks on power on every level of governance, down to local courts and state administration, which can be positive, in terms of preserving democracy, and can be negative, in terms of the tall order it is to try and enforce benign policies, such as the Affordable Care Act or same-sex marriage (if you think these are good things, that is).
An example of the opposite would be the UK’s Westminster system, which is still democratic but has an easier hand enforcing country-wide laws that don’t need to be endorsed and approved on every step of the way.
I must point out that I’m not comparing centralization/decentralization to unitary-statism/federalismm, because decentralization is possible in unitary states, and sometimes necessary, such as fiscal and administrative decentralization, and China would be a perfect example of this, where local administrations (in this otherwise extreme case of unitary statism), have a lot of freedom in collecting revenues and taxes and investing them in the way they see fit, sometimes even ending with a surplus at the end of the fiscal year.