In Vol. 3, No. 34 of the Hard2Guard Player Development Newsletter, I write about the crossover step. I use Roger Federer and Sandra Sinclair as examples of the crossover step in a sport-specific setting.
However, the video below shows the difference in speed in driving off your lead leg with a crossover step as opposed to stepping with your lead leg first. In the example, the athlete is faster using a crossover step than he is turning to sprint. This is not a perfect example to the difference between a crossover step and a traditional defensive slide, but coupled with the Federer and Sinclair videos, it certainly makes a compelling argument that in many instances, the crossover step should be the dominant footwork for defensive footwork.