Woooowwwww. The Beatles are absolutely spectacular in their original mono. It's not even close. It's such a rush to hear all the instruments all in one place, instead of being panned off to one speaker or another. I've never really liked that '60s stereo sound; more gimmick than anything. Jimi Hendrix and Led Zeppelin were the true stereo rock pioneers, I believe. The Beatles, however, focused on monaural for nearly their entire career, right up to The While Album in 1968.
To my ears, Magical Mystery Tour and The White Album sound excellent in stereo. There's a greater attempt to work within the stereo domain, instead of simply shuffling instruments to one channel and vocals to the other. That was the great crime against the earlier Beatles albums, and they sound soooooo much better in mono. I'm listening to Revolver and Rubber Soul, and for the very first time, I'm digging The Beatles as a rock band. Not a musically diverse pop group, but rock in the full, modern sense. Those albums knock your socks off the way The Rolling Stones and The Who knock you around.
Mono LPs enable stronger bass and drums, thanks to the grooves. This is one serious weakness of stereo, as any sound engineer will gladly tell you. You simply can't crank the bass volume too high, or that turntable needle will pop out. For this reason, mono records very often have more bite and growl in the low end. And you can hear that on the mono Beatles albums.
It's also a marvel to contemplate the skill and genius required to create layer after layer sound, and have it all come out of one sound channel. It's stunning to realize that 2- and 4-track technology was cutting edge in the 1960s. Just listen to Revolver or Magical Mystery Tour in mono, and just be amazed. George Martin and the EMI engineers were bloody brilliant.
Oh, and mono Sgt Pepper's Lonely Hearts Club Band is the greatest album ever created. But you should already know that.
Do whatever you can to get these 2009 mono remasters. They are absolutely spectacular.