I'm 50/50 on these two helmets and they are about the same price. I've always used Arai and I know that it fits. The Stilo looks pretty good and has a few features that the Arai doesn't offer but there is no local distribution so I'd have to order one to try it.
Arai
http://www.araiamericas.com/default....to/gp-6-ped-m6
Stilo
http://stilo-usa.com/helmets/st4-gt-w-carbon