Not sure on the fit. I haven't personally gotten to try an Airoh. I do know the LS2 fits the same as my Shoei, Klim, and Kali helmets I've owned if that helps.
On the Airoh, I've been lusting after one since I first laid eyes on the Aviator 2.2. However, after hearing how the pad foam sacked out on some rather quickly, and then the more serious rusting anchor issues, I decided it wasn't worth the risk to me. BTW, I have had neither issue with my LS2 MX470 Subverter after almost 5 years now. Been researching helmets for my next purchase and it will be the LS2 MX703.
Is your country a part of the EU? FC-Moto has it in stock currently and has been the best price I have found on it.
https://www.fc-moto.de/en/LS2-MX703-X-Force-Victory-Carbon-Motocross-Helmet