The first CANDIDE from 1956 is the best sung and played and indespensible as a classic OCR. Barbara Cook alone maks it worth owning but the CD is well sung and it is the only version to record the original lyrics.
It does not represent the show as it is now done on stage. The original Lillian Hellman book has been discarded in favour of a newer, sillier version by Hugh Wheeler. (That is not a slam: silly works well for CANDIDE.) Some of the lyrics were re-written by Stephen Sondheim for the 1973 Chesea theatre version which was out as a 2 LP set on Columbia but the label has never released it on CD. It has the whole show (as seen in that version - lasting about 90 minutes) but the cast are not strong vocally, and the reduced orchestra sounds skimpy.
The slightly revised version as presented by the New York City opera is out on a 2 CD set from New World but it dates back to the early days of CD's and may be hard to find now, though it is still listed as being in print.
Bernstein' conducted the complete 2-CD recording for DG not long before his death. This version restores material from all versions and has a good cast, but he takes the tempos so slow that it zaps all the energy from the piece. (Bernstein's recording of the opera CARMEN suffers from the same problem.)
The Broadway revival in 1997 was greeted dismissively, perhaps because New Yorkers had seen the show so many times at NYCO. I found the revival staged crisply and performed with zest and I quite enjoy the cast recording on RCA Victor. On a well-packed single CD they fit in all the key songs, so for a single disc its a good bargain.
I never tracked down the Scottish National Opera recording on TER, but have the DVD of the concert staging seen earlier this year on PBS with Kristen Chenoweth and Patti LuPone. For a concert staging it is rather inventive and does allow the music to shine, though I would have been happier if the 1986 telecast of the NYCO fully staged version had been released on DVD instead.
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