What's the greater evil - the risk that checks and balances fail and an evil person takes over, or that a federated system is unable to reach consensus and address existential threats like climate change or even significant but not quite existential threats like overfishing, pollution, war, and nonrenewable resources?
A more fair choice of options would be, "the risk that an evil person takes over" vs. "the risk that a federated system fails to address existential threats". The way you said it implies probability in the former vs. certainty in the latter.
An explictly evil person or group dominating the world seems like the greater evil in terms of outcome. That would literally be hell on Earth. When you look at probabilities, there's tons of examples in history, across thousands of years, of evil people inevitably rising to power when the system allows for it. Meanwhile, there are relatively few examples of humanity going extinct due to self-inflicted environmental damage.
Isn't federation one of the main checks and balances that keeps evil dictators from taking over the world?