Well, the actual system utilized in a society should be dynamically selected based on what works well. Democracy is one way to provide such dynamic selection, but the sad truth happens to be that truth tends to finish last, while factors such as money, information and sociology in general decides it all. The most immediate example, is the fact that my own very opinion is likely shaped more by the people I have known and the things I have experienced, rather than - you know - stuff that actually matters in a democratic context.
So, I have no answers, but I guess the point is that none of the systems on your list will ever work perfectly by themselves. We're all fucked.