Gilmour and Waters split vocals duties, similar to the song "Comfortably Numb" from The Wall (1979), and they represent different "characters" or points of view – Gilmour is the self-serving ignorant layperson while Waters is the intellectual, responsible observer of the world's woes.
Gilmour and Waters shared vocal responsibilities, much like in the song "Comfortably Numb" from The Wall (1979), where they portrayed opposing characters or viewpoints – Gilmour as the naive person and Waters as the knowledgeable observer.