For older songs, there are very many different interpreters of Robert Burns' songs, from those who sing in grand opera style (no thanks!) to those who almost turn them into rock'n'roll (think some versions of "Killiecrankie") and then there's the warbly, tune-changing, arm-waving versions by Eddi Reader which do nothing for me.
I prefer them sung in more of a folkie style: I'd include among the best singers of them Rod Paterson, Gill Bowman, Ian Bruce, Jean Redpath, Sangsters, Davy Steele, The Corries: and Steeleye Span did a pretty fair rendition of "Parcel o' Rogues".
As for "same song/different versions", there are a good number of Burns' songs that are not now sung to the tune originally chosen for them: it is interesting looking back at what the originals were, and whether the current tunes are an improvement: e.g. "Afton Water", "My Love is like a Red, Red Rose".