Just kidding.
Full face all the way. And not just for the great reasons listed above, but even if you don’t crash, you still have to deal with many hazards and items that get slung up in your face (water, dirt, rocks, oil, bird poo, roadkill, or my personal favorite, burning cigarette butts. those are awesome) I’ve even had an acorn smack me in the face when riding with a full face helmet and just the visor up (I got caught at night with a smoked visor…not fun). Plus, I have also heard that once you reach a certain speed, you actually get too much wind in your face and the helmet/ride becomes uncomfortable. As for ventilation, the worst time I have with a full face is usually just sitting at a long light or waiting on a train. Even then its not that bad, plus once you get going again, the airflow is great.
And if all that doesnt convince you, full face helmets just look badass. ’nuff said.