The stepper could be a much cheaper solution if it accomplishes the results you desire. A simple step and direction controller is much cheaper than a servo controller. Many high speed counter cards have a step and direction output that you can user to control the stepper controller. As the name implies the stepper motor moves in discrete steps, you can also step it half and quarter steps. The stepper motor is OK if you do not need high torque and do not need to control the torque. Stepper motors tend to run hotter than servo motors
as the amount of current the motor consumes is not dependent upon the load. Some controllers will let you reduce the current between steps, this would be OK if you do not need as much torque to hold position as to step to position.