The one to go for...
Ultra waterproof, ultra breathable. Even in <-10° weather I don't wake up with any condensation.
Fits my 0° bag great and once upon a time both my girlfriend and I slept in my 25° inside this bivy. Yes it was a squeeze but we fit!
How else can I say awesome... Has the right amount of stakedown points to keep it held down in any weather, one pole is plenty to keep the sack out of your face, and you'll never wake up wet. Is that okay?
And don't forget... never zip it shut all the way!
The picture included is mine next to my girlfriend's minimalist bivy... With 2 other OR bivys on the snow shelf below us. She has the OR Advanced now and loves it! A big happy OR family... And the warranty will work for my kids, because it's technically an "infinity warranty"... more than lifetime.