You can compare bivies all you want for specs; but actually using one with your gear is where it will matter. You'll need to try them out before if you have'nt owned one to see if it is 'for you'. Lots of people want uber lite, then find it too fragile, restrictive, etc. Think lying on your side cooking under your tarp while in your bivy. That makes a difference, as opposed to having to expose your sleeping bag to the elements.