Not a Beatles expert, but there are a lot of laserdisc editions; it could be possible to find out some mono versions, so I guess laserdisc higher S/N and dynamic could be a better source, at least in theory.
That would be an ok route except for the fact that only 5 out of 13 Beatles albums appear on laserdisc. Not to mention they are just the films. So you will get different edits and mixes than the album version and often songs are cut out of the film completely or are trimmed down significantly. For my purposes my original UK Monos are the best sources