Functionally the AMK v1 and v2 bivy's are very similar. The 2.0 bivy only reflects 80% radiant heat compared to the v1's 90% because the inside is lined and can oly be described as fuzzy. This combined with thicker (reinforced?) material, lots of velcro, a foot vent, etc. make it overall bigger and heavier. The v1 uses material very similar if not identical to their heatsheets (silver one one side, orange on the other).

I use the 2.0 bivy in my sleep system as a vapor barrier for cold weather and because it works so well on it's own in mild temperatures. I haven't tested the latter use yet but plan to this summer.

I keep the v1 in my shoulder bag as EDC fare along side my siltarponcho. I've never needed to bivouac emergency style with it yet...and I hope I never need to...but since it's about the size of an apple when bundled, I hardly notice it's there.

I also carry a regular space blanket with the tarp/poncho (cheap Coghlan's) as a ground sheet or a backup to give to somebody else in need.