Torque limiter question?

More "squeeze" per pad. There's also different sized pads, which can change things a bit. In a normal foot clutch scenario, six pads probably will last longer than four, provided the operator keeps the free-play adjusted when wear occurs. In a torque limiter situation, the Belleville spring only applies "X" amount of pounds of squeeze, so it can slip if suddenly overloaded, unlike a coil spring pressure plate which can have more squeeze than is needed, once the load is started moving.  A torque limiter is designed to protect the driveline from shock overloads. A-C isn't the only company to use such a device.  Deere and Case do for sure and probably others I don't know about.