Sanders is running on abject authenticity. I gotta say, I miss having someone so authentic in the race - someone who is going to say what he thinks needs to be said regardless of how it affects his poll numbers.
If the choice is between those three, well, I'm gonna refer to Hayek's definition of the Rule of Law - that the governing body absolutely has to be predictable. You need to be able to anticipate the actions of the state. And Sanders is certainly predictable.
I've stated before that I'm pretty sure not even the Gestapo nor the KGB would walk up to people randomly and gun them down in the street in a hail of 200+ bullets if they didn't think their conversation partner was showing the proper deference to their authority. In that sense, I believe that our state is less predictable than theirs were.
So I'm not really all that fearful of a man who openly wants to bring hard core communism to the US. If he says he's going to do it, he believes it, and we know what to expect and can plan for it.
I'm way, way more scared of a lot of the running Republicans than I am of Sanders.