A climbing helmet is always important to have on, whether you are cragging or mountaineering. You cannot predict rock fall, so be prepared for anything. A helmet's job is to protect your brain from rock or icefall. To a lesser extent, helmets can help in a leader fall, but most are not designed for that purpose. A helmet does no good strapped to your backpack while you are climbing, so put away the ego and strap up!
Plastic helmets are the most durable choice, making them perfect for beginners and anyone who knows they might get rough with their helmet. With a plastic helmet you don't have to pack them as carefully in your bag, and their lifespan will likely be longer. They are also the cheaper option!
Plastic helmets have either a strap suspension system, closed cell foam, or open cell foam. No matter what your absorption choice is, these helmets will be heavier and not fit quite as comfortably as a polycarbonate helmet.
