11 September 2018
I've always considered this to be primarily John's song if only because he sang it. Discounting the tunes they wrote for George and Ringo, the only other example (I can think of) of the main composer not being the lead singer is Every Little Thing .
I don't necessarily agree with the suggestion that John's always right about songwriting credits, and Paul's just bitter et al. After all John once claimed to have written most of the words to Eleanor Rigby , whereas others (i.e. Pete Shotton) have suggested he contributed sod all. As with most things, the truth is probably somewhere in the middle and I expect the same is true about In My Life .