Given that Sanders and Hillary voted in agreement over 90% of the time, implying close similarities, I’d take the more genuine and authentic of the two; Sanders.
On the Republican side, the only one running that seems remotely sane is John Kasich. I may disagree with him on a lot of things, but the other GOP hopefuls run the range between “train wreck” and “self-satire”. Watch this and you can see why he has my respect. Of course, that speech also effectively ended his campaign as it alienates the base of the party who think Ted Cruz is too liberal.