In the area that I generally work, I could not imagine not wearing a helmet. I am constantly in gusty winds that throw us around, and with the "superior" headroom in the 500, you should see the marks in my helmet. Granted the helmet reduces the headroom, but I would not have it any other way.
I agree with the better noise protection of the helmet, and I also use the "CEP" ear protection.
The passengers that I have, rarely ask about the helmet. My response is that it part of my uniform, and that seems to satisfy them.