hi,Using Step motor you can control smooth because it can be controled to rorate in small angles. But arcoding to my experience the ordinary motor may be stronger than step motor If they are the same RPM (revolutions per minute) .
the step motor can move to specific angles only varying the amount of voltage given to it during a certain time, it doesn´t move without energy which makes it perfect for small robots or precision designs.
The main advantage of stepper motors is that they can achieve accurate position control without the requirement for position feedback. In other words, they can run "open-loop", which significantly reduces the cost of a position control system.thus stepper motors are used where predefined steps have to be changes.