I think that in some contexts, like arguing over mathematical proofs (as orthonormal noted), spending a little time arguing with yourself to bring out X’Y’Z′ is polite and a sign of good faith. In other cases, I’d rather just trot out A’B’C′ early on, as long as it doesn’t require too much effort, and deal with both arguments at once without ever explicitly raising X’Y’Z′.
I think that in some contexts, like arguing over mathematical proofs (as orthonormal noted), spending a little time arguing with yourself to bring out X’Y’Z′ is polite and a sign of good faith. In other cases, I’d rather just trot out A’B’C′ early on, as long as it doesn’t require too much effort, and deal with both arguments at once without ever explicitly raising X’Y’Z′.