This is one of those songs that, no matter how many times I hear it, I still enjoy listening to it. If you were to ask me which was the best version I would just have to say, they are all equally great (each artist having stamped their own individual style on it). As for my own personal favourite I have to lean towards Judy Collins. I first heard this song almost 40 years ago outside on a calm quiet night, about 2.00a.m., and the acoustics were perfect. At that time it sounded like the most perfect song I had ever heard and that memory stays with me, even now. I have never heard it performed as well since (even though I have a copy of Judy's CD) - perhaps one night I shall sneak out of the house and try to reproduce that moment.
... and one last one from Nanci Griffith