Airtronics quality has slipped a lot the last two years on servos. They just do not last anymore unless they are servos that are over two years old.

Jr specs are usually very conservative on their servos meaning they are usually faster and stronger than the specs suggest. I would say Ko and Futaba are about the same as Jr so you can compare specs across the brands. Hitec's 5955 is a great servo and seems as fast as a Futaba 9351 but their older 5925/45 servos were trouble sometimes.

Currently I run Hitec 5955 on steering and Futaba 9350 (most bombproof servo ever but a little weak at 139 oz of torque) on throttle. I had a 9351 go bad after two races and another wear out the metal gears after a year. I'm not sure why they do not last like the 9350.