I'm about to buy a Waterfield Sleevecase for my 15" MBP. However, I'm not sure if I want the horizontal or vertical layout. I plan to get the flap, D-rings, and *possibly* strap if I can't find one laying around the house. There will be days when I only need the laptop and a few papers. What's your experience with either layout? Does it hold up better in either orientation? Does one feel more "secure" (I've read a few people saying this)? I plan to use both my messenger bag AND my backpack, so this is why I'm so torn. Which is the best multipurpose orientation?