While technically more of a backpack since it has two straps, the Ortlieb Velocity is by far the most waterproof of the bunch. It is a true roll top with a velcro roll closure to keep it that way. It has a padded back with vent areas for added ventilation. As an added feature it has a clip for a light or your helmet as well as reflective stitching for those night rides. Because it is backpack style it can also double well for hikes and with the handle makes it usable for carrying around the office. It’s biggest drawback for me is that it is not the best looking messenger bag, unless you want to showcase your bags durability.