Films

Both DVD and BD use the same transfer. Blu-ray is more cleaned up (hiss, clicks, pops) but loses detail in quiet moments due to noise gating and sounds less natural throughout.

4K restoration from Original Camera Negative

The old DVD's track has significantly better detail compared to BD, especially on the score. The BD has some extra detail on dialogue, but also exhibits strange artifacting (e.g. sample 3, 0:20) which suggests possible AI "enhancement" or some other form of aggressive filtering. In contrast, DVD appears to be completely unfiltered and sounds good throughout. Samples

As the BD is significantly rolled off, a lot of the detail (real or fabricated) is buried in the mix and not audible during normal playback.

Comparison, caps

Capelight's 5.1 is sourced from the original 6-track. The fidelity is comparable to the 4.0 from the 4-track available on previous BDs.
An alternate 5.1 mix was created for the 1999 MGM DVD / LaserDisc, It boasts better high end detail throughout, but the trade off is reduced bass.

See additional info for more detail.

West Side Story was produced as a 70mm Todd-AO presentation, with an accompanying 6-track audio mix in the following channel configuration: see diagram. 35mm presentations used a 4-track or a mono mixdown instead.

The original 6-track elements were thought to have been lost until they were recovered and restored in 2010. In 1981, for the film's 20th anniversary, a new 6-track mix was created by upmixing the available 4-track elements.

Capelight's release is sourced from original 6-track elements uncovered in 2010, but unfortunately it's not as detailed as it should be, owing to unnecessary noise reduction. It's by no means bad, but it could be better. As the Lc/Rc channels are mixed into into L/C/R, it's also essentially no different to a 4-track fold-down. This isn't exactly an issue as left/right center channels mix down to L/C/R very well, but a better way of handling this would be to use Atmos objects to position those channels where they should be, as Disney did on The Sound of Music.

The 4-track mix was included in a discrete form on MGM's previous BD, it trades blows with Capelight's 6-track-derived 5.1.

Interestingly, the 1999 MGM LaserDisc/DVD release includes a different 5.1 mix, which sounds a bit more detailed than the two other tracks. It's sound signature is on the brighter side, with a slight emphasis on the treble instead of bass like other releases. Although that accounts for some of the perceived detail, even after matching EQ there are spots where Capelight loses out. It's a slight upmix, with split surrounds and LFE. Whether it was derived from 4-track or 6-track elements is not clear, though it matters little, as the end result would have been very similar in either case. There are no booklet notes stating the source used, but it sounds very similar to the matrixed 1992 LD, which was attributed to the 6-track. Still, given that the original elements were thought to have been lost, I would assume that this refers to the 1981 mix.

Previous LaserDisc releases are similar to the discrete 1999 track. All LD releases are missing the intermission music and a brief whistling sequence.

The 7.1 upmix on MGM's Blu-ray offers little of value.

For the most part, the mono track available on the BD and UHD is fine, but there's an 8 minutes long segment which sounds terrible with artificially expanded frequency range causing very audible artifacting. The 5.1 remix doesn't have that issue. Sample

Disney 3D Blu-ray has a slightly better audio mix

Cinema DTS-ES centre channel information unconfirmed

Sony 4K Blu-ray has the original theatrical Dolby Atmos mix

From 4K restoration but exhibits compression artifacts

Both cuts are excellent in 4K. See caps

Director's cut: 2007 WB Blu-ray; Arrow is a lossy transcode with dynamics compression.
2007 BD's AC-3 track with dynamic range compression enabled is nearly identical to Arrow's, see comparison

Theatrical cut is fine.

The "Remix" remaster has slightly different cuts for some episodes, and completely redone audio mixes. The original TV version of the English dub also has an entirely different audio mix from either the Japanese mix or the "Remix" remaster.

Italy Dynit Blu-ray or Japan Bandai Blu-ray each have their own pros and cons, and completey different transfers

BFI Blu-ray (slightly)