Work as well as an OEM mirror for seeing what was going on behind.
Would be indestructible. It would have to give way in a crash to avoid damage not only to the mirror, but also to the bike.
It could fold completely out of the way, so that when you are offroad, you don't have to think about it.
Both models hit all three marks right on the nose. DoubleTake uses SAE spec glass to give maximum visibility (it can be important to distinguish Crown Victoria headlights from other vehicles!), it is made in Colorado Springs from a super tough nylon that comes with a lifetime warranty (on the housing, not the glass, but you can buy the glass seperately), and sure enough, it folds right down when you want it gone.
If you're deciding between the Adventure model, and the Enduro, our advice is simple. If you plan to fold the mirror down a large percentage of the time, the Enduro is right for you. The long size means the head of the mirror tucks away right behind the headlight. If the mirror will more or less remain extended, get the Adventure- the more compact design is more stable at highway speeds. Either way, you can't go wrong.