We can tell you that in reality, all the vans built with the "look of off-road", our so called Competitors, are close in weight.
In general, the wood frame builders are heavier than our vans with aircraft style frames, from the trailer assembly up. They have to have larger wood beams across the roof to support the air conditioners and such. We are lighter from the wall frames up. We are heavier from the trailer assembly down because of the body armour and the larger suspension. Overall we are about the same weight, our weight is just on the underside rather than the top in walls and roof. Because of that, in the Bushtracker the centre of gravity is lower than with the rest, but we all weigh about the same..
On the matter if what weight you can expect to tow: We weigh them with the major gear you picked, solar panels-batteries etc, on board, where Others might call it "optional equipment" or Owners cargo, and weigh it before installing that gear. We only want to do the right thing, and weigh the vans with all that equipment on board because the Owners need to know. If you take most of our Optional Equipment, it weighs in about 300- 400 kg. For instance our AGM solar block sealed batteries are over 33kg each, three of them are 100 kg alone! But anyway, in all sizes we weigh the vans with that Optional Equipment installed. If we are heavier than another van in the same size, it is mostly the Optional Equipment we offer, not in the van itself.
In 16' with a lot of gear on board, we have seen weights run about 1900 to 2000kg or a little more. In 18, if you put a lot of gear on board, you can expect to be at about 2.3 tonne. Allow more for extra water tanks and such that will push your overall loaded weight over the 2.5 tonne mark. And with most of that Optional Equipment on board, a 20' can weigh in at 2500 kg.
Some vans will weight a couple of hundred kilos more in each category, if they opt for extremes of equipment, like 4-100 AH batteries, and 4-125 solar panels for powering up a fridge in the tow vehicle, and flat screen TV, and things like automatic deploying Satellite Dishes and such... But again, this is in the Optional Equipment category of gear people have added, not in the van itself.. However, rolling on 16" truck tyres and wheels with our suspension is a lot easier than rolling on normal caravan suspensions; and weight in the case of Independent AND Load Sharing Suspension, is not such an issue. Windage and aerodynamic profile is probably a more relevant concern with respects to fuel economy for most Tow Vehicles....
In Summary the Myth Buster: Our vans are not heavier, we just usually have more Optional Equipment on board, and we weigh them fairly.
Regards from the lone Ranger, Myth Buster....