OVERHUNG allows for greater coil winding height(more wire surface area on the coil for heat sharing, some of which is out of gap), where there is usually better power (heat) handling and the woofer is more efficient (more efficient because same amount of wire stays in gap throughout excursion range).
UNDERHUNG has smoother transition of magnetic properties through normal use, but limits power(heat) handling , and is less efficient.
So... Overhung is a bit more reliable....especially when abused.
copied from Termpro forum