I'd just like to say that my boss has one of the clear cases on his Vita, and they're really not as bulky as they look in pics. I've been considering picking one up for mine, especially since it will still fit in my "Pull 'n go Folio"
I don't think that having an always-on case is worth the added bulk for a minuscule chance of higher durability during a fall. The Vita is substantial enough that the thickness of a snap on case on the unit sufficient to protect the Vita from a decent impact would seriously bulk the unit up Nd make it much less enjoyable to use. I've never been a fan of screen protectors either.
This pouch will certainly protect your Vita during travel as well as carry along everything else you will need.
I also got the Official Vita Screen Protector, which went on super easy without air bubbles. I put it on crooked but that was my bad. It's worth $10 if you want a protected screen.