If you don't need the extra weight carrying capacity at the back, it's always better to have single tires.

That way, the back tires run in the tracks created by the front tire. This provides better traction and lower rolling resistance.

If I couldn't get the payload capacity from single tires, and I was going offroad a lot, I'd go up a size in vehicle - rather than get a dually and introduce a whole new set of problems.