Your descriptions of their styles (sarcastic-vs-optimistic, whiny-vs-syrupy) are reasonable for their lyrics, but this analysis seems to focus only on the instr

Your descriptions of their styles (sarcastic-vs-optimistic, whiny-vs-syrupy) are reasonable for their lyrics, but this analysis seems to focus only on the instrumentals, the melodies, chords, and so forth. Their lyrical differences are reflected in the melodies, of course, but I would not describe Lennon's chord choices as "sarcastic", for example.