Who sings reflection from mulan?

One of the two:

Christina Aguilera

Lea Salonga

It's actually Lea Salonga, in the movie. Christina Aguilera did a twist of the song, but it's not the same lyrics, anyways.

They were both good in their own way. Christina is a powerful belter, if a bit pop-singer "nazely" sounding, whereas, Lea has a trained Broadway-style type voice.