Larger profile
More flash or contrast
More vibration (pressure waves)
More hooks (even a swipe and miss on the body can hook a fish)
Pushing or pulling is a matter of boat setup, and of course both can be done at the same time.
The occasional Black Crappie is caught on cranks, but for all intent and purposes it's the White Crappie that's the main target. They tend to suspend in open water more than Black Crappie, and the Crappie follow Shad schools as they roam over channels & flats. Maximum depth is determined by a thermocline (if present).