Arai helmets are more compact on the outside. this was a tip offered by Girlsbike2, for the same bubble head reason as you mention. I don't worry about it massively as long as the lid fits, but it is a consideration if there are 2 different brand helmets that fit equally well.
I am five foot tall and my AGV looked huge on my head, as do Shoeis (if i can get them on). My Arai Astro is a lovely shape
I've tried Suomys on and these fit lovely but the dealer i was trying them on in didnt have a decent mirror handy so i couldnt check out the aesthetics
