I was just rereading Three Worlds Collide today and noticed that my feelings about the ending have changed over the last few years. It used to be obvious to me that the "status quo" ending was better. Now I feel that the "super happy" ending is better, and it's not just a matter of feelings - it's somehow axiomatically better, based on what I know about decision theory.

Namely, the story says that the super happies are smarter and understand humanity's utility function better, and also that they are moral and wouldn't offer a deal unless it was beneficial according to both utility functions being merged (not just according to their value of happiness). Under these conditions, accepting the deal seems like the right thing to do.