I've used Defense 4 bags for 15 years, got my third one now. I've occasionally used several high end mountaineering down bags, and rugged Wiggys bag, but for me nothing beats the Def 4 for safety and comfort when sleeping rough. It is perfectly windproof, drastically reducing the need for a proper shelter. And it is water resistant enough for you not to care about rain or melting snow. This thing is just perfect in a snow hole as well as on the side of a bare mountain. The zip never catches and never fails. The absence of a collar helps for quick operation and is not an issue in practice. I can't imagine myself taking responsibility for a group at night in tough weather and using anything else than the trusty Def 4 for me to return to.