yeah so wouldn't you want an anteanna that has some gain to it?
If the gain is achieved by making the antenna directional (like a beam), then you would only want that if you need to cover one airport or set of transmitters, and you are far enough away that an omnidirectional antenna won't provide the gain you need. Airborne transmissions are easy to pick up, even if you have a beam pointed in the opposite direction.
If you only want to pick up airband and you want omnidirectional coverage, you're best off building your own vertical dipole, j-pole, or other type of narrowband antenna.
Most people want to listen to a wide range of frequencies...that's why the discone and Scantenna are popular.
But that GroveBeam III is a very fine antenna, if you have the room for a beam antenna and you need to steer your gain in a certain direction. Works like a charm.