There are only 3 axis.
Period.
roll, yaw and pitch.
The 6DOF LSM303 I have is a triple axis magnetometer and a triple axis accelerometer.
For the 9DOF, a triple axis rate gyro is added.
How you get 9 axis is beyond me!
I went for the 6DOF with my ROV because a 2 axis "compass" is not accurate unless it is level.
For my UAV I'll go for a 9DOF sensor.
Once you get off the ground having a rate gyro is all important.
I have more of an issue with dropping "rate" from gyro.