I choose both! Zuko rescues Aang but is too injured to pull it off without eventually resorting to his firebending, thus revealing his secret identity and sending everything to hell in a handbasket.

Sokka: "...I think it might be frog-induced hallucinations, but I see a dead Zuko on the floor."
Aang: "You should check your eyes, Sokka--"
Sokka: *sighs in relief* "Tasty frog, though."
Aang: "--because Zuko's just asleep."