As for "musical differences," I've seen some people argue over the years that it was McCartney's "Maxwell's Silver Hammer" that drove John, George, and Ringo over the edge. As it happens, I like the song though it wouldn't make my my Top Ten list of favorite McCartney-penned Beatles songs. More on the song from me here: https://lyonsnyc.medium.com/maxwells-silver-hammer-93b65b074f7b