The Nonesuch studio cast is the best and most cmplete OH, KAY! around.
Same with EMI's excellent 1991 BRIGADOON, which includes a lot of the dialogue. I have always preferred Columbia's studio cat with Shirley Jones and Jack Cassidy. It plays like a cast album if the show had opened in the mid-1950s. (It is mono, recorded just before the full switch to stereo - but as with other Columbia albums of the era, has a full rich sound.
RCA Victor's OBCR has poor sound quality and the performances don't really come across with any theatricality. (To be fair, it was Victor's first OCR.)
Cast albums are NOT "soundtracks."
Live theatre does not use a "soundtrack." If it did, it wouldn't be live theatre!
I host a weekly one-hour radio program featuring cast album selections as well as songs by cabaret, jazz and theatre artists. The program, FRONT ROW CENTRE is heard Sundays 9 to 10 am and also Saturdays from 8 to 9 am (eastern times) on www.proudfm.com