I really never liked step sparring much. At least not the kind that my first TSD school did. For that, one partner would go to an unnatural set position (low-block, front stance), while the other partner stood in an unnatural set position (a ready stance with the hands down by the waist and the feet parrallel and facing front), then, with yelling to signify being ready to avoid anyone being startled ('cause that never happens in the real world), the low-blocking partner then would step forward and punch while stepping into a front stance (moving from A to B, no in betweens, no footwork, no random movements), the defender then blocks, parries, attacks, or whatever. Yuck! I am so glad I don't do that anymore.
I prefer drills. They can be done in 1,2,3,4, etc. steps. Two opponents working together, with differing levels of resistance, to learn techniques and series of techniques. I like to have both opponents begin from a defensive stance (like the type I would take on if I am at a bar and some jerk starts getting violent), though there are many various ways to get things going. Then the partners drill the techniques together. Sometimes back and forth, sometimes one person only. Sometimes I'll let them experiment and try to see what works and what doesn't. It's the best way to go in my opinion.