I like to call 0 rebound " dead shocks".
I can tell more of a difference in offroad with building your shocks with rebound or dead. The dead shock build seems to make the buggy jump more shallow and roll threw the bumps. Buggy shocks built with rebound jumps a bit higher and seems to feel it rolls over bumps verses rolling threw the bumps.
As for onroad goes. I would like to think the car would be a bit more responsive with shocks with some rebound. I would not think anyone would never want full rebound for onroad. I always run some rebound but I am always trying to find a more reactive car.