Aang having the privilege of growing up with airbenders all around him and learning airbending straight from the monks in his temple but having to live the rest of his life as the last air nomad with no one to share his culture with.
Vs
Katara having the privilege of still having her people and culture but not ever being able to learn southern waterbending style because she never met another southern waterbender and only knowing the northern way of fighting and also having to grow up quicker.
Aang wishes he has the community Katara has and Katara wishes she had a childhood Aang had.
