Stepper motor control is the most cost-effective way to control a machine tool. The accuracy is exceptional, and the price is very reasonable. The only limitation is that the maximum speeds for rapid and cutting moves are not as high as for servo control.
Servo control uses feedback from an encoder to constantly monitor the machine tool's exact position. Using the feedback signals, the control system can achieve very high speeds and exceptional accuracy, even under very strenuous conditions. A servo motor essentially has the ability to correct itself it is ever out of position.
The difference between stepper and servo control can be explained using the analogy of walking through your home in the dark. You know how to get from place to place, but you go move slowly because you don't want to lose your position and bump into a wall. This is like a stepper motor. If you instead turned the light on, you walk much faster because you are getting constant feedback from your eyes with respect to where you are. This is like a servo motor.