Well, personally I love both.
My daughter is
Hannah, and had my son been a girl, he would have been
Emma.
If I had to choose I'd go w/
Hannah. To me it sounds cute on a little girl, yet grows into a sophisticated name as an adult. Hannahs meaning "graceful" is better (imo) than the meaning of
Emma "universal". Plus... the palandrome thing is kind of fun!
You can't lose either way... but my vote goes for
Hannah.