Samuel told Saul that obeying the LORD is better than what?

Answer: Sacrifice

"Obedience is better than sacrifice, and attentiveness is better than the fat of rams" (KJV: "to obey is better than sacrifice").

“But Samuel declared: “Does the LORD delight in burnt offerings and sacrifices as much as in obedience to His voice? Behold, obedience is better than sacrifice, and attentiveness is better than the fat of rams.”— 1 Samuel 15:22 (BSB)