the safety ratings are pretty dubious at best, because one helmet can be approved of in europe, but not in the US, or vice versa.

As long as you buy a helmet from a reputable maker, you're safer than without one.

you obviously want a helmet that's not too heavy, because it's can be a strain on your neck with the extra weight.

other helmets you might want to consider are MTB full face helmets.

One thing the snowboard/ski helmets seem to lack are proper ventilation for the amount of work you do on a bike. Riding a bike is more effort and more sweaty compared to skiing or snowboarding.