My full face greatly reduces my field of vision which MIGHT cause an issue in an emergency but, in that same emergency, such as when I got hit head-on and bounced off the front of the van and flew through the air only to land head first, it can also save my ass (and my head). Didn't do a damn thing for the broken bones.
My full face is fantastic when it comes to sealing out cold and wet and hail and noise which is why(only reason at the time) I was wearing it when I kissed that #$%*'s van in my lane.
My half helmet is great for keeping my bald head from getting sun burned and abiding the law in CA & NV but wouldn't save my face or jaw like my full face did.
I still prefer choice, my choice and not someone else's. If I finally get my fool ass killed when not wearing my helmet, well, that's choice, my choice. Please call me a stupid dead f@#k if that happens because that will be true. Stupid AND dead.