Adventure Med bivy vs Blizzard Bag

Have narrowed down my winter emergency bivy to these three products. I'm trying to distinguish the differences between the three. Has anyone had any use with any of these. Trying to compare the three in terms of durability and warmth. Have not used any of them. Looks like positive reviews for all. Will use for single day ascents in case of emergency. No sleeping bag. Will use in a snow cave.

1. Adventure Medical Thermo-Lite 2.0 Bivy

http://www.shopatron.com/products/productdetail/part_number=0140-0223/453.0.1.1

2. Blizzard Bag

http://www.blizzardsurvival.com/product.php/100/blizzard-survival-bag

3. MPI Extreme Pro Tech Emergency Bag/Or MPI Extreme Pro Tech Bag (Essentially look the same)

I appreciate the suggestion of the Blizzard Bag and MPI Bag from previous post. Just trying to narrow down the choices between the three now. Thank you.