I strongly recommend helmets for all snowsports, both skiing and snowboarding. I've personally witnessed (and experienced) head injuries with both.
The benefit of snowboarding is that you are much less likely to have a horrific injury like a major leg bone shattering. Most injuries tend to be cracked tail bones or broken wrists. With the latter, you can learn to fall correctly and that minimises the risk. Essentially you want to fall on your arm, and then roll onto your shoulders and back instead of taking your entire weight on your hands.
I 100% agree. As a beginner skiing person 5 years ago, I once went way too fast and had a very small (natural) lamp. I made a backflip and hit the back of a rock with my helmet and landed in the snow.
How does this happen? I fell down on the button lift and was forced to ski down from the button lift in order to enter the lower part of the piste. I thought I had enough skills to do it, but instead I lost all control and went straight down and eventually was going out of bounds, flying in the air hitting the rock with my head mid-salto and flying into the far edge of the lower (blue) piste area.
That helmet saved my head that day, I had zero injuries, not even a mild pain. In hindsight, this was a really fun experience! (in hindsight)
I was a loose projectile as a beginner, and it took quite a while to learn how to become a guided projectile.
The benefit of snowboarding is that you are much less likely to have a horrific injury like a major leg bone shattering. Most injuries tend to be cracked tail bones or broken wrists. With the latter, you can learn to fall correctly and that minimises the risk. Essentially you want to fall on your arm, and then roll onto your shoulders and back instead of taking your entire weight on your hands.