servos
while yes a metal gear upgrade exsists you stand the chance of tearing up the servo motor. then your talking about replacing a 115 dollar servo for the sake of one bad run for a 3 dollar plastic gear is it worth it? thats up to you. certainly if it happens at a big event and cost you a good qual. run or a podem in the main then that sucks but still. those servos are not free either.
good luck