Ewan MacColl once described the traditional ballad as having "the economy of verse" and because these noble songs tell a story I personally find them far easier to learn than say a six verse piece with no tale to tell. Since the OP asks which ones; The Outlandish Knight, Tam Lin, Minnorrie, Hughie the Graeme, Fair Flower of Northumberland, Lord Gregory, Lord Bateman and Child Owlet are among those that I do.