The waterfield is just too wimpy.
Braincell is pretty cool but the top "Closes like a cereal box"??
If your sleeve is going into a snug briefcase (does anyone still use briefcases anyways?) maybe the thin neoprenes and waterfields are OK. But I carry a canvas messanger back to school (KU - Go JAYHAWKS).
I'm bouncing all over campus with thick psych books slamming my thighs all day. I take an art class and have pencil shards, chalk bits, etc down at the bottom of my bag. This is why I sprung for the Vyper - and I'm a poor college student
But my MB is the most important possession I have and I had to demand three things from a sleeve:
1. Ruggedness and Durability - Neoprene does not these things have.
2. Total Enclosure - no flap holes / cereal box designs etc.
3. Style - I have a reputation to think about