I just did a search and went to Servo City..It is a site that helps you decide what type of servo you need ..According to them Karb servos are 5 times stronger than nylon..and metal gears wear out several times faster than nylon. It says MG servos have two Cons..Weight and wear.....To start my search I typed in Metal gear servos if you want to check it out... It also talks about their motors etc...