My opinions--yours will vary:
Cushioned pin boxes will help reduce chucking transmitted to the truck. A cushioned suspension will reduce shock to the trailer and reduce chucking to the truck. In our experience adding the MORRyde pin box reduced checking 50% and their SRE4000 rubberized equalizer reduced it to a total of 98% gone. I suspect that the equalizer first would would have had a dramatic effect by itself. I strongly believe that reducing the shocks to the trailer will help it last longer before shaking apart. Pin boxes with vertical motion dampening may help reduce the shock felt in the truck--I have no experience.