Whats your preference?
I've never had anything but the seat-belt type fastening on my crash helmets, but the new lid I bought today comes with the double d-ring. And as I stood in the shop fumbling with these arcane bits of metal I couldn't help thinking why anyone would prefer this method to the speed and convenience of the seat-belt ones. D-rings just seem to be an unnecessary pain in the arse; I even had to get the shop bloke to show me how you do it after my initial attempts failed. And to add insult to injury when I finally got it done it proved even more fiddly to undo again.
Obviously after a bit of practice it won't be a problem (hopefully) but it does seem strange that this method of fastening is still chosen by manufacturers over the speedy 'clunk-click-iness' of the seat belts.
Do the d-rings have inherent advantages over the seat-belts? Is one method more secure than the other? Or does one of the Directors of Arai own a D-ring factory on the sly, and is just protecting his investment?... Hmmmm