He outmaneuvered Orochimaru. Orochimaru was arrogant and assumed that all he needed was one shot to take over Sasuke's mind. Sasuke must have known that was Orochimaru's ultimate goal (it had been for what, two hundred chapters?) and once Orochimaru got there, he was able to turn the tables on him, not just defeating him, but stealing his power for his own. That seems to me a much sounder defeat than simply killing an opponent.

Also I'm curious that you only responded to one word of mine, do you not have anything to say about the rest?