Fit is measured, not guessed
Laptop sizes are diagonals, and two 15 inch machines can differ by an inch in width. Measure your laptop and compare it to the sleeve dimensions, not to the marketing size. A bag that fits a 15.6 inch Dell may not close over a 16 inch MacBook Pro.
Padding that does something
What protects a laptop is a suspended sleeve, one that keeps the machine off the bottom seam. A quarter inch of foam glued to a flat panel does very little when the bag hits the ground corner first.
Strap and hardware
A wide, padded strap distributes weight and stops the bag from sawing into your shoulder. Metal hardware at the anchor points outlasts plastic clips, and those anchors are where a loaded messenger bag fails first.
