@Abingdonboy
Bro, having owned Storme (and old Safari and Scorpio before that in my family) I can say that they are both too heavy for sand. At least the 4x2's are. Unless you know how to keep up the momentum, are experienced and know where not to go, and have at least one jeep (or tractor) within call, it is easy to get stuck badly.
You need 4x4, and both (but esp the Storme) need to go on a serious diet. But yes, as mechanical platforms, they are solid, rugged, tried and tested (in Indian conditions, for close to 2 decades now), good power, good reliability, good fuel efficiency, and infinitely customizable.
Both have done very well in both the Raid de Himalaya as well as the Desert Storm rallies, though racing over bad terrain for 7 days with full backup and doing what these army mules do is a whole different ballgame.
The Gypsy is still the undefeated King of the Raid. It is less than half the weight, is petrol, and is very nippy. So I do not see that role going to another vehicle. Not even the new Renault Duster or Nissan Terrano.
Do check out the Mahindra Thar or the Force Gurkha for these roles instead.
Though frankly, the venerable Mahindra MM550 is still the undisputed King here.