We bought a double axle trailer with leaf springs and an equalizer between the wheels. The equalizer allows the tire to still stay in contact with the surface when one wheel falls into a dip. The equalizer lifts the other wheel by the same distance as the deflection. So, the load on each tire stays about the same. The contact patch for each tire stays about the same. That seems safer.
Last month, we towed the trailer on a four mile "shortcut" back to the campground that was a road where the pavement disappeared and they quit grading it five years ago. The "beast", as we call our half ton Silverado towed the trailer well. I could tell that the trailer was staying where I put it and it didn't move left or right. Everything was in good shape when we got back to the campground.
I have a hunch that the rubber inserts in torsion axles would degrade after a long period of such harsh treatment. I suspect that there would be slop and backlash in the handling since the suspension is based on rubber that is always preloaded.