As was mentioned, give them a call. I did and chatted for quite a while with Gary (don't believe it was the owner Gary but another one) who was very helpful. As I recall he said the wider bags are warmer because of the way they drape around you and maintain loft rather than when you press against the sides of the bag with the narrower bags. That's comparing the Kodiak versus the others. No idea on the Versalite? Call, they are very cool about helping you out.