Cedric and Bertrand want to see a movie. Bertrand wants to see Muscled Duded Blow Stuff Up. Cedric wants to see Quiet Remembrances: Time as Allegory. There's also Middlebrow Space Fantasy. They are rational but not selfish - they care about the other's happiness as much as their own. What should they see?
Sure, but there's still a meaningful question whether you'd prefer many moderately happy puppies or few very happy puppies to exist. Maybe tomorrow you'll think of a compelling intuition one way or the other.