We just back from our trip it was -35C and we have a chance to compare all 3 helmets Oxygen, BV2S and Modular 3 for 2 days at same conditions.
So Oxygen seems all good a little bit moisture on bottom of wiser, not big deal, so my friend pretty happy with it.
I'm a little bit sceptic if electric parts fail during a long trip, you are done...
My other friend has BV2S and he has a problem with freezing valves and as result fogging visor, so he was forced to use heater, with out heater no way.
I were Modular 3 no fogging except sun visor so not big deal I just did not use it. I plugged in my helmet at end of he day when my exhaust holes was frozen and I feel difficult to breath and I didn't like to take off helmet and clean it, so I just plug heater.
So my opinion is Modular 3 is still simple and reliable helmet for long run.