I agree that the whole was greater than the apparent sum of the parts, but I still rate Paul as an enormous talent and wish I could see him perform live(-ish, with 900 computers 6,000 midi devices and an army of techs).... The other point is that even though they largely wrote alone, especially in the last half of the Beatles, I think the competition and ultimate collaboration that went on in the studio improved each other's writing and songs. When solo, I think the both suffered ...
The one variable / catalyst that was removed from the partnership when the Beatles broke up was George Martin whose musicianship, discipline, commercial ear and producing talent was key to their early success. All of this allied with the raw talent already in the partnership and the work-ethic they developed in Germany was an unstoppable combination.
Some of the early "give-away" songs seem difficult to reconcile with the balance of their work, for example the bossa nova rhythms of Cilla Black's Step Inside Love (attributed to McCartney but with both credited) and certainly the output of Lennon-McCartney song-writing factory did a lot to raise the profile of the "Mersey Sound" independent of their own record output. Early recorders of Beatles originals (as distinct from covers) included Billy J. Kramer & the Dakotas, Chris Barber and his Band, Peter & Gordon, P.J. Proby, Mike Shannon, The Rolling Stones and many more. Arguably this could never have happened without George Martin's influence and contacts.