Neither. Aang is a holier than thou pretentious condescending moralfag who doesn't even have the maturity to find a third option between killing and not killing (Aang could compromise with villains, attempt to befriend them, defeat villains without killing them, etc.) He's incredibly naive and immature and instead of growing, the narrative and GOD ITSELF literally rewards and enables this narrow minded behavior that doesn't fit the world he lives in.
Korra is insufferable, gets everything handed to her and barely works for it, and yet STILL FUCKS UP EVERYTHING and stagnates as a character for three books until they chose to "fix" her by torture porning the crap out of her, when nothing actually changed on a fundamental level. Her behavior stayed the same, only her tactics changed.
She and Aang both have their character arcs FUCKED UP because of Bryke having a bias for them.