1. both doors are operable
2. they do not use ball-catches. I need something with real (pet-proof) latches.
Regarding #1 - I prefer that the design does not require one door to be "locked" shut in such a manner that requires multiple steps to undo. Our exterior French doors have a nifty pull-up-on-the-door-handle method to latch the one door to the frame before the other door closes against it.
Definition: interior = between two rooms. exterior = between a room and the world.