Initially, we take longer steps to open up the lower body, to develop flexibility and strength. After that the steps should be natural. The waist controls the legs, they do not move independently.
This allows easy stepping in which the cross energy can easily be accessed and applied. The danger with a long step is that you can find yourself stuck in one leg, unable to sink quickly into the other one. Smaller, more natural steps allow for greater mobility.
The application of cross energy is a dynamic process, with energy stored in the legs and controlled by the waist. This can get lost with long steps.