Q: Aside of Madoka's goddess form, rank the magical girls by their power.
A: Mami > Kyouko > Sayaka. It depends really on the situation though, while Mami is really strong she goes down easily when she doesn't pay attention. Homura is the strongest when no one finds out how she uses her powers.
(Gen Urobuchi, Nitro+ Q&A Panels at Animagic 2013)