Are some motors more powerful than others?

Various types of sewing machine motors:

Many years ago there was only one option, that was an AC electric motor, very much the same as the old Singer 201k had in the 1950's. Newer models, in particular computerised sewing machines, can offer a DC servo motor version, (Alternating Current vs Direct Current). Let's delve deeper in to the differences between AC and DC sewing machine motors.

• AC motors: Need to spin/rotate at a greater speed, to gain the same torque, or piercing power to the needle point. In other words, you need to sew fast trough thicker materials.
  
  
• DC servo motors: Fitted to computerised models, are smaller and more lightweight, yet have a bigger torque spread. You can sew is a very controlled way, as fast or as slow as you are comfortable with, and the needle will get full piercing power, even at slow speeds. They may be about 40% the size of a AC motor, the DC motors can easily power a sewing machine forward or backwards at high-speeds, and with more power.
  
  
• Servo, means, the motor takes feedback from other parts inside the sewing machine, before it drives the belt, shafts and eventually the needle.