The truths of literature and what you might call “the Straussian truths of the great books”—what you get from Homer or Plato—are at least as important rational choice ethics. But the people who do rational choice ethics don’t think that. If the two perspectives aren’t integrated, it leads to absurdities— problems like fanaticism, the Repugnant Conclusion, and so on. Right now though, rational choice ethics is the best we have—the problems of, e.g., Kantian ethics seem much, much worse.
If rational choice ethics were integrated with the “Straussian truths of the great books,” would it lead to different decisions? Maybe not—maybe it would lead to the same decisions with a different attitude. We might come to see rational choice ethics as an imperfect construct, a flawed bubble of meaning that we created for ourselves, and shouldn’t expect to keep working in unusual circumstances.