Or "I never get to sing this song. You wouldn't either, if you had the option I have."
As a songwriting team, of course their influence overlaps, but I have heard them say that the process is often quite linear. One person starts a song and the other fills in the blanks, or makes suggestions.
I think I have heard Dave say that he wrote "The Way It Will Be" a,d "Elvis Presley Blues." What else?
(Maybe there should be a "misc" forum section)