With the motors internally geared with torque we get about 1 ball every 1.5 - 2 seconds. If you look in one of the pictures you can see another catapult arm laying down. Both catapults are functional and exactly the same so when using both you get about 2 balls every 1.5 - 2 seconds. If motors were internally geared toward speed one catapult arm could get about 1 balls every 1 second.
Using the video you posted at reference my catapult has about the same accuracy. Out of all the preloads we average about one ball missing every time either due to the ball not settling correctly on the arm (human error) or sometimes ball density.