The vast majority of our duffel testing is done in "real life". We travel, organize, and live out of these duffels for weeks and months at a time. Our test team moves around a ton and largely lives on the go. If this team can't find a weakness or perk, we don't know who can. On top of the day-to-day use, we conducted a few objective tests.
Ease of Transport
We examined each bag for its carrying options. We consider grab handles, suitcase handles, backpack straps, long shoulder strap, and integrity when dragging along the ground. The primary asterisk here is that it is not our habit to test gear to failure. Dragging bags with a standard load until the fabric wears through would be excellent testing, but that would be wasteful. We can deduce dragging durability from real-world use and material selection.
Ease of Packing
Regular use draws out the pros and cons here. Further, we look for the main opening shape and size, stiffness of the fabric (does it stand up when empty, for packing and unpacking? Does the fabric fight back as you try and stuff it full?), and accessory pockets.
Most of our information on durability is deduced from the team's long and thorough understanding of materials and construction techniques. Since we do not test to failure, we cannot actually fully assess durability. However, we are confident in our assessments based on deduction and abundant real-world use.
We weighed 'em. On a calibrated hanging scale. In communicating weight in the review text, we also correct for volume. Since not all bags are offered in the exact same volumes, it is difficult to compare all options directly. Nonetheless, we can make very astute deductions to help you select a product that isn't any heavier than you need.
Routine use of virtually every single one of the tested bags involved exposing valuable contents to wet weather. We learned good things about them therein. Further, we filled each with towels and bedding and hosed them down in the driveway. When a bag claims to be submersible, we drive it down to Idaho's Teton River and dunk it under for testing.
Our methodology is thorough but not overly clinical. We emphasize "real world" use and find that we can make the best assessments this way.