The obvious point here is that history matters. If you don't preserve them exactly, you'll lose the history.

On the other hand, people always modify songs in performance -- they sing them in their own accents, often with their own particular vocabulary words, and in ways that conform to their vocal and instrumental abilities. So you can't reproduce them exactly.

So I would say the true answer is, "Sing them your own way, but acknowledge your sources, and encourage people to look at those also."

That being said, I do think the greater value is in retaining as much of the old as possible, because it is history. If you aren't retaining the history, then what's the point?