Well, obviously aang. korra had all that time to master elements, while aang mastered air fully at a young kid then mastered all the others in just one summer and was able to beat ozai who was actually said to be virtually impossible to beat.
The obvious choice is Aang .Because he's more experienced.
He had to battle the fire lord. Um... did Korra do that? No.People who say Korra probably didn't watch the original series Avatar:The Last Airbender.
korra master water fire and earth at like 6 and did not master air til 15. aang mastered air at 11 and mastered water and earth at 12 then mastered fire at 13
korra took down the spirts at 16 and aang beat oazi at 13 korra had more time to master the elements so her. either way they're the same person hello .....avatar