[legionof7]

I'm pro-decentralization for a lot of things, but one big benefit of centralization is speed. It's a lot easier for one "node" to change something than a whole system.

A real-world analog would be like a dictatorship vs a democracy. The dictatorship can make faster decisions but the democracy often makes better decisions.

[gitgud]

I think one of the reasons decentralisation makes better decisions, is that every node has equal say in the decision.

Whereas a centralised system may not ignore a lot of the nodes when making a decision.

[fastdev]

Isn't this also its biggest drawback? If every node has equal say we need to have additional complicated logic to ensure consensus, while in a centralized system we do not need to this, since a centralized system is a source of truth and the only writer?

The same logic applies to less decentralized systems like NEO that have a predefined set of voting nodes. Less nodes, means that we need less effort to achieve consensus, hence higher performance.

So the question is: in what use cases truly decentralized systems cannot be replaced with not so decentralized systems?

[gitgud]

Precisely, centralization provides a simple architecture for the system.

However, since all the power is concentrated to one "source of truth", it can lead to unfair decisions for the rest of the network.

Decentralized systems are ideal went you want to ensure there's fair decisions for the whole network. It's much more complicated to build, but worth it in some cases eg; crypto currencies, governments etc.

Also it's not strictly a black and white categorization, systems can have levels of decentralization; eg: the internet