The BMF originally came out in an 8 inch version, either sawbacked or plain back. The blade shape is reminiscent of a Randall No. 1. Cutlery Shoppe requested that a nine inch version be made, with only a single guard, called the Predator, I think? After that, Gerber changed the regular model to be 9 inches as well.
The LMF originally was made in a 6 inch drop point shape, but was changed to a shape similar to the BMF. Both models could be either plain or sawback.
The BMF sheath is quite heavy, as it includes a diamond stone and a compass, but the knives are of reasonable weight. You do want to carry them on a web (military) belt, as the sheath and knife together are weighty. This didn't stop me from carrying them for years in the backcountry (still do when I'm in the real backcountry and feel like a sidearm would be nice).