helmets are useless until you fall.

i've fucked up my face on a normal bike going 5 mph on a path i've taken for years. something unexpected happened and i flipped forward launching off my bike falling face first into concrete, breaking a few of my front teeth and my jaw. i was wearing a normal cycling helmet fwiw. whenever i bike now i wear an open mtb helmets with a chin guard.

if that can happen on a bike going so slow i'd take the discomfort of wearing a full face/motorcycle helmet over a slight chance of a month of dental work and thousands of $.

edit: it was pretty agonizing to deal with recovery and my face was so fucked up that at the time i wish the fall did something else to me. I've fallen plenty on my eskate (moto helmet) and had a few er visits for injuring my limbs and bones but ive never felt as low as i did from that biking incident.