I love the small vault style cases (both the black hard mesh and metal) because they fit easily in my shoulder bag. But sadly, my Why 8.0s and 8.1s don't quite fit in the small vaults.
I just use the soft case for normal daily activities, and just put them in a bag in a strategically protected area. If you need to throw them in the bottom of a bag or suitcase, I would just use the larger vault, and throw in a second pair of glasses in there. It's not so large that I would be too concerned about size.