The size of the motor is measured in horsepower and is often given more importance then it merits. In a shredder, a portion of a motor's power must first be applied to overcome the friction and internal resistance of the cutting head and drive train before any remaining power can be used for shredding paper.
This is why oiling increases the cutting
capacity; reduces the friction of the
cutters, and more power remains to cut paper.
In a precision built shredder such as Dahle's, ball bearings, precision aligned frames, and a sealed oil-filled gearbox work together to minimize the internal friction created. The result is that more of the motor's power is available for shredding paper and a smaller, more efficient motor can be used to obtain the same results.
A competitor having a larger motor may not be providing the user with any additional speed or cutting capacity (true benefits to the user). The larger motor may simply be required to overcome the internal friction caused by inexpensive design or flimsy construction.