I know that you guys offering opinions already know this, but for the guys that are just learning about trailer suspensions, dampening and geometry should be mentioned also. Shocks can be used with most any suspension and may have relieved some of the issues that guys are pointing out. For example, add shocks to leafs or torsion axles and they will behave very differently. The springs are only part of the equation.
- Springs (leafs, the rubber inside a torsion tube, torsion bars (different from rubber torsion axles) air bags, etc...) support weight, that's why properly choosing and loading springs is so important.
- Dampening (shock absorbers) control the motion of the springs and how the springs react to different terrain.
- Suspension geometry determines the motion of the axle as the suspension cycles. Torsion axles move back and up, as the springs compress. For the most part, leafed axles move up and down. Moving back and up will be better for deeper pot-holes and whoops and have less benefit for washboard.
All this given, if you don't want to figure all this stuff out on your own, I'd recommend buying a suspension from someone you trust.