It was touched on, but the solid axle increases the traction in an off road setting because when one tire is up on an obstacle, the other tire is forced into the ground providing more traction. Conversely, when an IFS tire is up on an obstacle, the other tire is not being force onto the ground, it will just go to its limit in down travel. This is well illustrated with the two pics above. The H1s front right tire is just hanging there providing no additional traction. The jeep under that shows that the downforce from the tire up on the obstacle is what's driving the tire into the groung for added traction.

I've seen H1s take bypasses around fairly technical trails that lightly modified, thinner, shorter wheelbased vehicles could overcome.