I am a member of another bike forum, every year around summer there is a discussion concerning open face lids,it's always a hot topic.
It's all down to personal choice, I wear a full face, but have had an open face in past and probably would wear an open face again in hot weather for a gentle cruise etc.
A friend came off his bike several years ago,broke an arm and shoulder,then slid face first into a curb stone,which resulted in him shattering his jaw and losing about a dozen teeth, and yes knowing what happened to my friend I would still wear an open face,albeit just for occasional rides, day to day rides(ie normal riding/commuting) I would wear my full face.
At the end of the day,I know the risks,and I'll take my chances,but then we all do that every time we ride our bikes.