I plan to add emergency bivvy sacks to my car's kit.

Does any of you guys (and/or girls !) know the difference betweem those two products, found on Aeromedix web site :
- Thermo-Lite Emergency Bivvy Sack
- AMK Headsheets EmergencyBivvy Sack

Is there any difference in thermal isolation, re-usability, strength, aso... ???
<img src="/images/graemlins/confused.gif" alt="" />

I have already replaced my old survival space blankets, with new AMK orange survival emergency blankets, which seems much more stronger and larger.

TIA