In the world of big rigs, duals are the standard. They also have a minor safety advantage of allowing the vehicle to remain in control and mobile enough to pull off to the side of the road, if one of the tires has a blow-out. Super singles are favored in applications where maximum load capacity is required. By law, most states limit big rigs to gross 80,000lbs. To carry more weight, you have to reduce the weight of the truck. Super singles are capable of carrying as much weight as standard duals, but duals tend to be heavier. The super single design, along with other weight saving components allow some trucks to carry more physical weight without exceeding the max gross limit.
In an off road application single tires tend to have more advantages than duals. For one, it's difficult to go wider with duals. Space between the tires need to be maintained to prevent wearing out the sidewalls, especially as you air down. Also, mud and other off road debris, can pack up between the tires and rims, greatly increasing unsprung weight and causing severe unbalance. Tire maintenance is also increased with duals. Tires should be at equal pressure at all times.
Ed