5600U or Radeon 9600 Pro? I'd take the Radeon any day. Image quality and performance more or less destroys the 5600U.
Again though, I'm not too sure about ATI's drivers, Nvidia have proved to be reliable with thier drivers throughout (apart from the little cheating incident in 3D Mark 2003
) wheras ATI have be renowned for poor drivers (even though they are improving loads).