I've got access to copies of both box sets.

The mono set doesn't include Abbey Road, Let It Be, and Yellow Submarine. In addition, disc 2 of the Past/Mono Masters set contains about half different stuff.

In addition to the differences between the Past/Mono Masters disc, the Mono set also contains the original stereo mixes of Help and Rubber Soul. I can't figure out if these are the new remasters or not.

The stereo separation on the Stereo versions of Please Please Me and With the Beatles is still miserable. The rest are fine. I haven't done any A/B comparison on the rest, which were originally mixed competently.

It's notable that the only included album that wasn't originally either UK-only or worldwide is Magical Mystery Tour.