I've used a female avatar since I reached tour legend and was gifted one. Everyone in our club is sent one when they reach that milestone. Not sure why it started but it's carried on to this day.
It used to be that the female had more movements, for some weird reason, and could be more accurately used to control power. I'm not sure the avatar movement difference exists any more. When they reduced the number of frames in the swing they must have reduced the reliability of this method anyway.
As Sting says though, with most clubs now having free shot and putter pal there's much less reason to use avatar movements anyway.