The purpose of this is that you use these cells only for KAP and keep the batteries as a receiver set and a transmitter set. Charge the TX cells as soon as the indicator on the transmitter says to do so. The receiver batteries need to be recharged when the airborn system stops responding to the transmitter. Taking good care of your batteries will that they last long and reliable. And of course they cost more and need a charger that supplies a higher current.
More advanced chargers offer discharging circuits, peak detection, and rapid charging.
Their only disadvantage of standard size servos is weight. They bring 40 to 45 gr to the scale. Examples of standard size and micro size servos. A well-balanced rig will need far less torque than one that is out of balance. Micro-servos reduce the weight of the rig and your purse.