Is'nt up too you on what you like too put on your head? Any helmet is better than people I see that still don't wear one.
As for the Mountain bike helmets, I am pretty sure that Giro makes one that is DOT approved. I have raced pro dh mt biking for many years and have taken some really nasty crashes smashing into rocks, trees, one that comes to mind is the crash I had going over 50mph, the helmet is still fine just a few scratches and one real shakin up me after stopped from bouncing off rocks. I would use one snowmobiling seeing the abuse they can take.
Also is it not that after every crash or impact on your lid you should check it for any cracks, dents, etc. If so you should be replacing it.