Have you read "Tune in - vol 1", Mark Lewisohn's epic Beatles tome? Only takes you (from 1940) up to the end of '62, but the detail in it is amazing. Still waiting for "vol 2" some 5 years later!
Lennon was unquestionably leader of the gang through the Hamburg years and on through to about '65, when McCartney started to really hit his straps. McCartney was infinitely superior as a musician IMO, but Lennon gave the band their edge, and the dynamic between the two of them was extraordinary. The ultimate demonstration of a combination being exponentially greater than the sum of its parts.
The McCartney/Harrison friction is well documented, but after watching 'Get Back' I don't think the Lennon/Harrison dynamic was any less testy, and if I'd been Harrison when Lennon started sneering in his face about "I me mine" I'd have told him very forcefully where to go.
Yeh, the music thing and the City thing go hand in hand, don't they? The Beatles and City have both been life-long obsessions for me and if I ever had to give one of them up, I'm not sure which one I'd choose!