HTC M9 camera better than Sony Xperia S?

I heard that the HTC M9 camera isn't very good.
My sister want to upgrade from Sony Xperia S to the M9.
Had someone the SXS before and can tell me if the m9 camera is better than the SXS or even worse?
I mean, HTC M9 has a 20 mp camera yes, but Sony smartphones always have good cameras.