Well, in my very limited experience I feel that discos are not at all good for soft sand specially when it comes to steep climbs & need for momentum. Otherwise its an excellent off-roader. Lack of acceleration compared to its bulky body and narrow tracks makes it a no no for dune bashing. It has ample torque to climb a mountain straight ahead if the ground has enough traction.
On the other hand TLCs have much better acceleration, larger tires and wider tracks that really help the driver to maneuver the vehicle on crazy angles.
Defenders & FJs are loved for their known performance as carriers of water, fodder, & luggage etc off the road.
In stock condition, the best performers I have seen in soft dunes are:
SWB - Wrangler (newer models) & Nissan Safari (Patrol)
LWB - Land Cruiser & Nissan Safari (Patrol)
