C902 will have a far better camera. The G900 is a smartphone with a touchscreen and hand-writing recognition - better overall phone but no edge, HSDPA, or GPS.
Unless you have a home set up, then probably not for the wifi, but UIQ3 is an excellent OS. You can get it for R149 a month on MTN Anytime 100 while the C902 is just R20 less. Personally I would pick the G900 simply because there's lots of cool stuff you can do with UIQ and it's quite user friendly.