The biggest strength of autocracy is the ability to be more long-sighted. Democracy, taken to it's natural extremes, leads to a system where you have representatives spending most of their time in office planning for the next election, which is to say fund raising and focusing on things that'll pay-off before the next election cycle.
So you get an obsession on the very short-term stuff, and a tendency to trend towards oligarchy (though Plato would claim it trends to tyranny).
But the problem with autocracy (that monarchy only exasperates) is that a single bad leader can undo generations of achievements of skilled leaders. Aurelius was one of the wisest and most capable leaders to have lived. His only son was one of the worst.
Democracy's weakness is it's strength there - even the most inept (or perhaps senile) leader can't do that much and they'll be out of office in a few years anyhow.
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Also, as I seem to end up debating with you in these little geopol threads often enough - let us hold one another to our predictions. Told ya on South Korea. ;)