Whilst the illusion of a degree of democracy can make people feel empowered and involved, democracies tend to be fickle and unfocused.
Giving people, often with limited clue what they're doing, power, just because they want it is a recipe for disaster.
A benevolent dictatorship, with subordinates appointed based on merit tends to be the most efficient form of governance.
An alliance establishes a core set of values and from then on its about implementing them, people joining the alliance sign up to those values and the associated objectives; if you don't like it, find another alliance; if the leadership is incompetent and suffers from too much megalomania to step aside for the good of the alliance, find another alliance.
Its an interesting debate but something of a no brainer, sure leaders should be accessible and open to debate and discussing things, especially with their more capable advisers (and good ones will generally seek such advice) but in high pressure situations, people need to know who's in charge and do what they're told.
(Suggestions of specific numbers of each post are quite frankly laughable, its good to be able to delegate and spread the burden, especially if this provides 24/7 leadership coverage, but a lot depends on the size of the alliance, the time leaders are prepared to put in [and how much of their own playing time they're prepared to sacrifice as a result] and how many capable and trustworthy people are available in an alliance, after all there's no point in appointing fools as anything but a court jester [I believe that would be 5Gods in NU]).
Interesting discussion, but in the end its a no brainer, you need clear leadership, beyond that its a case of whatever works and how good people are at their jobs.