The efficiency of a centralized system depends a lot on the speed with which information is transmitted and the processing potential of the central node, as well as the ability of the system to reshape itself in the event that the central node is removed. Generally this last achievement can be achieved through backups, in robots this could mean each robot has the potential to be a central node in the system, with biological organisms you'd likely see multiple competing hive's or otherwise have backup rulers that lie dormant till needed. You probably wouldn't want all of your eggs in one basket, but let's assume that's the only option for a centralized system, why might you choose that over a distributed system anyways?
In some circumstances centralized systems can be much more resource efficient and can be far superior in terms of decision making. With a decentralized system each node is only aware of it's surroundings and the signals of others, in a perfect centralized system the central node can be aware of all of it's drones surrounding's and can formulate complex strategies for the hive as a whole and execute them with perfect precision. A distributed network is a cheap knockoff of actual omnipresence and relies on signals propagating through a network of multiple intelligence's, but with enough processing power a centralized network can be the real thing. Essentially a single god like entity in total control, similar to plugging our nervous system into a nations infrastructure. 198
However, if information moves through the network too slowly or the central node can't process all the information efficiently, the system loses it's edge.
Beyond that regard, it's also potentially a waste of resources to have every drone capable of thinking, it's especially wasteful if each drone is highly intelligent. If you assume that each drone is intelligent and communicates with every other drone the processing required will increase exponentially with each new drone, whereas a central system only has to send the information once for each drone, then send a response. A caste system addresses this somewhat as a hybrid system, but is still not as ideal as having a mind capable of correlating all the information of the hive at a quick pace. If it's instead a simpler form of communication that creates emergent intelligence, that could be more resource efficient, but is not as likely to manifest in the same level of intelligence, nor be as adaptable as a conscious entity.
Given very fast information processing, a centralized network can get away with using less resources per drone and less processing per drone by potentially an exponential amount, by keeping the communication at a linear rate per drone. This allows for further expansion of the hive. So if a hive is primarily concerned with growth, centralization probably allows for the greatest growth per unit of resources until the distance become too great for rapid communication. So the answer is that it's only the best option when you have the necessary processing capabilities and a means to send information almost as fast as the nervous system because omnipresence and super intelligence is a very powerful combination that might outweigh the risks. 198