[altis]

Radio reception is all about signal to noise ratio. The signal is from the transmitter is the bit that we want. The noise comes from other sources that are working on the same frequency and, obviously, we want as little of this as possible.

Fitting a booster amplifies both the signal and the noise by the same amount. The S/N ratio stays the same - it's just louder. We can achieve the same effect by making the receiver more sensitive. Actually, we are quite good at this so, in most cases, there is little to be gained by boosting the signal. One exception is where you have a long download and you fit a booster near the aerial. This will help suppress any noise ingress.

On the other hand, if we fit an aerial with more gain then we actually increase the signal to noise ratio. This is because the aerial is more focussed in the direction of the transmitter and receives less signal from around about.

Ergo, high gain aerial gives lots of benefit whilst a booster gives only marginal benefit.