The Giro Omen is better than the G10. While the G10 is more comfortable than the Omen (more padding), it's vents 1) only have one control, and 2) are deeply recessed into the helmet. What the recessed vents do is collect snow (when it's snowing obviously), then when you open them for some ventilation, pour cold water on your head, resulting in instant brain freeze. REALLY uncomfortable.
The Omen's vents are much more flush with the helmet, and you can brush the snow off with your palm then open them.
When the temps are in the mid-20's to low thirty's often I need to open the vents at the bottom of the hill, and learned this lesson the hard way.
BTW, the Giro Fuse is even worse for this situation (even deeper vents in the shell), so be advised.
Oh, also, when you mentioned brim, remember that you have to pull the goggles over the brim - on some helmets it's barely doable.