I'm a patroller at a mid-sized mountain in New Hampshire and we have no rule where patrollers are required to wear helmets, or people that ride motorcycles either. After all, NH is the "Live Free or Die State". But I wear a helmet and the vast majority of my 80 patroller colleagues do as well. A week after one of them started wearing one he had a bad accident at one of our mountain's other resorts in Vermont. The helmet likely saved him from a potential TBI. I remember getting hit in the head with a chair after being thrown from it in a freak lift accident when another person and I were carrying some heavy gear. I was glad I had one on that day when I saw the damage to the helmet. There have been other times for me, and I'm a decent skier that has passed all the senior patroller skiing and toboggan requirements. So it's just a matter of time before each of us wishes we had one on.
This past Sunday I was first on-scene for an accident where a 21 year-old went off a 15 foot triple-jump without a helmet. I can't say that the outcome would have been different with a helmet. But I suspect he will wear one in the future if he ever skis again. I've never skied once in the last 10 years without one. But I can confirm that some patrollers have even cited junk science in our own magazine, supporting the view that people are actually just as safe without them. So this debate will likely rage on forever.
Coincidentally, I just bought a new one after 4 years, and in that short time the technology has gotten 100% better in terms of fit and function, in my view. That was true for the manufacturer I purchased from each time (Smith). And I wasn't even aware that it could be better, because the older technology seemed fine. I'm sure the same is true with most other manufacturers. I find that it's best to get the goggles and helmet from the same firm. The integration and fit are better and they function better in terms of not fogging-up. The adjustable vents on top are amazing and the warmth is reason enough to use one, and most coats can fit the hood right over the helmet with no visibility issues in extreme weather.
Most importantly, get the right fit and keep the chin strap firmly snapped. There is no point having one on when those two conditions are not met, and I can assure you, it will fall off and present a hazard when you need it most if not properly fit and attached.