Agree. Rubber will absorb more impacts than poly. Poly just translates it into the next touching material (ie, metal). Poly will last longer, no doubt, but it also costs more. I'd even go as far as to replace your transmission mount and motor mounts. Just go to the parts store and get the stock replacement. They're rubber.
Remember, though. It's still a Jeep. You can only smooth it out so much.
Corey