One of the major advantages of using the Air Squib is that it is activated with radio control. No cumbersome switches to hide allows the actor to fully focus on acting. An off-camera technician sets off the effect by pushing a button when the actor is perfectly positioned.
A radio-controlled hit means that the actor can really look “surprised” and shocked then the hit appears. You avoid that involuntary “squinting” that often occurs the second before an actor himself pushes a hidden button. In other words, you get better performance by the actor, when you use a radio-controlled unit!