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