Regarding getting hit with 5000 lb of plastic or metal. Its not entirely a good analogy, but if you had a choice between getting hit with a 5000 lb concrete block or a 5000 lb sack of styrofoam peanuts at 40mph which would you pick? Until someone gives me good reason to do otherwise, I'd take the peanuts. They would "give" and absorb some of the shock unlike the concrete block which is going to make me do all the "giving".

Getting hit by a vehicle isn't good any way you look at it, but the steel bullbar is apparently a lot more rigid than the plastic and certainly a lot more rigid than the original sheet metal. The more rigid the vehicle, the more damage its going to do to the pedestrian in a typical situation where it doesn't literally run over the person. Plus, the pipes on the bullbar are going to concentrate the force more if you hit them.

I read somewhere that some of the european countries were considering bull-bar bans because of the additional injuries they cause to pedestrians.

Alan