“If you look at the lyrics McCartney wrote after the Beatles broke up, they tend to be rather tame. Lennon added a certain pungency to McCartney’s music.”
On the other hand, I would think that one would have to look at the relative successes of McCartney’s and Lennon’s careers after the Beatles split.
McCarney’s career flourished while Lennon’s tanked.
This is why some refer to the Beatles as Paul McCartney’s first backup band.
Lennon had Yoko.
Career-killer!