Venting
I own a $20 Schwinn helmet I bought at Target and a $100 Giro E2.
In the summer when it is 100degF I can not tell that one is hotter than the other. Seriously - my head is hot not matter what. This is true at 90deg too.
In the winter and cooler months the Giro feels cooler, because I can feel the cool air on parts of my scalp. But I don't really need the cooling as it is cooler out.
The Giro is a bit lighter, but no more comfortable.
The Giro looks better.
I am glad I have the Giro. I do feel a bit bad though because of buying such a marked up product.
Al