I have an old MLD eVENT bivy that see's limited use anymore (mostly winter in snow shelters) with the advent of cuben shelters. The MLD bivy weighs 12 oz (the OR Alpine bivy you mentioned is 2 lbs!), my solo cuben tent weighs 18 oz with stakes- replete with bathtub floor, decent vestibule, bug netting and plenty of room to stretch out- doesn't make much sense for a bivy with these features for roughly the same weight (or less than some bivies).

The only advantage I see with a bivy is the size of the footprint; if you were planning on camping in very craggy/rocky areas (maybe mtn goat hunting???) then it might make sense. My shelter has a pretty small footprint and hasn't been a problem finding a place to set it up.

[Linked Image from imgur.com]