Mobile movies. MP4 or Real Media?

Recently I am learning about video formats
for mobile devices like Smartphone or PDA.
After trying compressing and converting some
of my video and music files. I learn these thing:

  • AMR-NB codecs is bad. You certainly not going to get
    enjoyable experience listening to sound in this codecs.
    Unless it is purely speech.
  • MPEG4 video with AAC audio is very good but it has big size and
    only playable in newer model of mobile devices
  • Real Media is good however it is very proprietary.

So what video format should I choose? Any good advice?