WLD's point is also the reason there can't be a simple "best." I agree with Alanabit that it should be part of the analysis of what makes a song "work" -- how well does the writer pull off what he's trying to do?
Comparing songs like McColl's with Earle's head to head might be pointless, but both could be studied in the same workshop with reference to the songwriters' apparent intention. In fact, I would suggest that a song that promises to be traditional sounding but unintentionally wanders off into a modern social commentary would probably be a good "bad example" for the workshop. That is, if I could think of one, I would suggest that. ;-)
-HM