the edition with the glossy, coloured covers (1987) is the result of the editing efforts of Peter Bartok, Bela's son. the brown and beige buff covers are the much earlier edition(1940), published when the composer was still alive. the original Hungarian titles are not translated identically for all the songs, for most the English name remained the same, but some differ, for example no.110(vol.IV) is 'Clashing Sounds' in the 1940, but the 1987 carries the rhythm of the original Hungarian more fully, 'And the Sounds Clash and Clang'. the 1940 edition does not translate the titles and notes into German, the 1987 does. this possibly was a result of the German language editions being controlled by Bartok's original publisher in Vienna, Universal Editions, or simply a matter of editorial choice, given Bartok's decision to emigrate knowing life in the shadow of the fascist empire was already intolerable when he left, in Hungary soon becoming worse. in his private letters he expressed awareness of what fascist totalitarianism would bring even before Germany began invading its neighbors, and after Austria was 'annexed' into the Reich, Universal Edition under 'aryanization' sent registration forms to Bartok (and Kodaly) requiring them to verify their ancestry/ethnicity.
the back covers of the 1987 edition have an autographed photo portrait of the composer, the 1940 lists all the song titles from the six volumes.
there are probably more editions of Bartok's work available now than ever before, when rights belonged either to Universal Edition or Boosey & Hawkes. for obvious reasons Bartok himself could not fully catalog, organize, edit his archives, which extended into ethnomusicology for cultures now assimilated or severely reduced by nazi 'purification', when he emigrated to the u.s., and much of his time in the u.s. he was ailing physically or simply scrabbling for a respectable livelihood. material from the archives is available now through several publishers including Dover and Editio Musica Budapest. Peter Bartok himself had to persevere with twenty six years of litigation to secure rights to his father's manuscripts.