Enrique,

The inrunner makes a lot of revolutions (about 40.000) and needs a gearbox to let the prop run at a usefull speed for F3A purposes.
Here the magnets run inside the cage with the electric coil.


The outrunner does not have a gearbox. The prop is fixed to the housing or the axis and makes the same rpm as the motor.
Here the hull of the motor with magnets run outside the coil that is in the center of the motor.