After trying most of the readily available (in NZ) helmets on I found that they had such different shapes that you really need to find one that fits correctly rather than worry too much about anything else. I found that the Yes helmets fit was a bit too big around the sides of my head, and that the NZI helmets were just not comfortable so I ended up with a Bieffe - which is just right - light and comfortable. I could not try on the Shoei or the Arai, because they are not readily available over here, and I didn't want to order something as critical by mail order (and they cost far too much!!! NZ$900 - ouch!!). I think that the Bieffe helmets are distributed by Parts Unlimited in the US, so they should be available from just about any dealer. However the Shoei is probably a better quality helmet if you can afford one - just be sure to try one on first!!
Good Luck.