Personally, I wear an Arai Signet. Arai makes various helmet patterns (Signet, RR7?, Quantum, Astral, etc) and they all fit different shaped heads. The Signet is the only helmet which I have found which truly fits me well, even when trying on Shoei, HJC, AGV, etc.
If I am not mistaken, Arai makes three different size helmet shells, were as most other manufacutures make one shell size. As a result, you get a more properly sized helmet shell rather than somthing which is simply stuff with other "stuff". Result, Arai helmets are more balanced than the other brands IMO. Try palming an Arai helmet on your flat open hand on the side (approximately where your ear would be) of the helmet and then try another brand. The Arai stays on your hand, others tend to roll off.
Arai is in the process of doing away with mail order purchasing and is going only to dealer sold helmets. No more internet orders for Arai helmets. Each Arai dealer must stock a minimum of 12 helmets and SHOULD be knowledgable in the proper fitting of an Arai helmet. Arai is working on this at the current time. A good dealer will help you obtain the proper Arai model, as well as help you with alternate cheek pad thicknesses, and in the case of some models, help you with changable top liners.
Whatever you do, whatever brand you decide on, make sure the helmet you purchase fits correctly and is Snell safety rated. DOT safety ratings are a joke.