>The problem is that human benevolence is fickle, and subject to interpretation
Basically, the "benevolent" half of the "benevolent dictatorship" is a long-shot at best and a total fantasy at worst. I think this is well-understood by reasonable people, but I'd also argue that "dictatorship" in this context is even more of a fantasy.
>An autocracy could make these trade-offs without political consequence
See, I don't think this is true at all.
Nobody rules alone, every dictator needs enforcers, those enforcers need enforcers, all the way down, and suddenly the well-oiled autocracy that can cut through red tape like butter looks more and more like it requires an endless hierarchy of "benevolent" (i.e. compliant) dictators or a bureaucracy overburdened by rules that was supposed to be democracy's great weakness.
Every decision you make as an autocrat is a gamble that your enforcers will carry out your vision faithfully, with a bunch of details you haven't even thought of also accounted for, while maintaining the facade that you are actually all-powerful.
All it takes is a few slip-ups for your underlings to have flexible loyalties, where "of course" you're in charge but maybe next time leave some wiggle-room for an alternative path of implementing your omnipotent decrees.
Basically, the "benevolent" half of the "benevolent dictatorship" is a long-shot at best and a total fantasy at worst. I think this is well-understood by reasonable people, but I'd also argue that "dictatorship" in this context is even more of a fantasy.
>An autocracy could make these trade-offs without political consequence
See, I don't think this is true at all.
Nobody rules alone, every dictator needs enforcers, those enforcers need enforcers, all the way down, and suddenly the well-oiled autocracy that can cut through red tape like butter looks more and more like it requires an endless hierarchy of "benevolent" (i.e. compliant) dictators or a bureaucracy overburdened by rules that was supposed to be democracy's great weakness.
Every decision you make as an autocrat is a gamble that your enforcers will carry out your vision faithfully, with a bunch of details you haven't even thought of also accounted for, while maintaining the facade that you are actually all-powerful.
All it takes is a few slip-ups for your underlings to have flexible loyalties, where "of course" you're in charge but maybe next time leave some wiggle-room for an alternative path of implementing your omnipotent decrees.