For the young, the beautiful and the brave a full-face downhill helmet is probably mandatory to prevent disfiguring injuries and a lifetime living alone.For the average mountain biker airflow is probably key. I know there is an argument for the weight, the colour, the shape, the name or the graphics but when you pedal up a long, steep hill on a hot summer day with the sweat stinging your eyes then airflow counts.The best helmet then is the coolest.
Until your hair begins to disappear or turn grey and things change. Because then you do not fall off and bounce instead you fall off and land like a crumpled jacket. It may not seem to hurt at the time but that is probably due to age related nerve damage or living in your own space-time and that is also, why it hurts the next day.
So you consider some shin pads and full finger gloves but a full-face helmet has to be avoided because if you turn up anywhere with the look of someone who hucks then that is exactly what everyone else expects you to do. You could continually make excuses that it is only for protection but who would listen.
The other downside is pulling off your helmet at the end of the ride and everyone else recoiling in horror at your “locked in the sauna overnight” face. However, there is another option.
A Parachute seems to be an Anaxagore with a chin guard and it looks a bit heavy and constricting but it is not. Surprisingly it does not feel heavier than my V Element when riding and my field of vision is not restricted. The weather is somewhat cool at the moment so summer riding might find a limit but at present it is no hotter. The rear adjustment is a simplified version on the V Element and the internal head shape seems identical. The front chin bar is not restrictive when riding but hydration tubes, energy bar, and even ham sandwiches enter from below and not through the face opening. It is a little tighter to put on and remove so measure your head for the correct size or you will have to ride with folded ears.
So overall no downside but is there a benefit. Yes. The reassurance from the extra protection means that you can try an obstacle or two and concentrate on the task at hand. You may still fall off and it may still hurt tomorrow but you will not bash your face and you may just protect some very expensive dental work and that makes it cheap at the price.