It didn’t work out so well for the Athenians...

My naive guess (as someone who is not at all a historian) would be that democratic states historically tended to have more functional economies and thus won wars more often.

On the other hand, democracies can be particularly susceptible to demagoguery during wartime. This is what caused the collapse of the Athenian empire (at least if we’re to trust Thucydides’ account).