Biggest benefit I believe is their ability to start working again if you submerged in water during an enthusiastic off road session. They are also a pain to strip and clean if said water is also full of mud, it stays inside turning to grinding paste it you do nothing.
This is my experience on my drum only series Land Rover. That said if you keep them above the water they are very effective and not sure you can claim a disk is a better handbrake. This is based on my VW (disk handbrake) which would move overnight if parked on a hill. :laugh:
As to the handbrake on the Jimny conversation specifically, I would at best have expected it to be as good as the original shoe system. It should hold the vehicle on a steep incline, if it can't then something is possibly wrong.
Yokohama Geolanders, Sony head unit, NAUTILUS Air Horn, DRL conversion, Rear cargo space, Elvis Bobblehead, transfer Guard, Indian hanging Elephant, Koni Heavy track dampers, Custom SS exhaust, Voodoo Doll, Adventure Rack with LED ight bar, vintage ERIBA caravan usually attached (yes it's slow)
