I would agree with those who feel classical arrangements of folk songs often lose a lot. When listening to such an arrangement, it's a question of whether you enjoy the style of the arranger, rather than whether you like the original folk song--since there will be far more of the arranger's flavor than of the original song.    Like some other posters, I also have a foot in both camps. And I'd have to say I far prefer the original songs by and large.   Though I really do enjoy the Vaughn Williams folk song suite--for orchestra or band.   And some others of his settings.   Especially what appears to be the standard arrangement of "On Linden Lea"--though the dialect is of course missing in the version I have bought.    Vaughn Williams appears to have been the most successful composer in giving folk songs another life--but maybe that's just since I like his style in general.

My large choral group recently did a CD of Grainger arrangements. I'd have to say the only arrangement I thought was successful was the "Air from County Derry."    Perhaps it helped that it was wordless--the chorus just an instrument.

But Grainger had some truly wacky ideas, to my mind.