Going through the brand is the fastest way when you already know what you're looking for. Each backpack brand has its own specialty, warranty duration, and spare parts policy that explain the price difference.
A backpack brand is judged on three verifiable things: the specialty of origin, which explains the shape of its models, the warranty duration, and the availability of spare parts. The rest is a matter of taste. The backpack brands below cover different uses.
Each brand comes from a trade, and you can see that trade in its products.
The most sought-after backpack brands are compared on facts, not reputation: the Eastpak backpacks and sport models do not target the same use. A backpack brand is chosen based on use, never on the logo. At equal format, three questions differentiate two brands. Does the warranty cover the zipper, which is the first point of breakage? Does the brand sell replacement straps and sliders, or do you have to throw away the bag? Is the back offered in several lengths, or is it one size fits all? A clear answer to the three is better than a logo.
A single brand often covers multiple uses, and two of its models may have nothing in common. If you're still unsure, start with the volume in litres and the carrying type, then go back to the brand for differentiation. It's the order that provides the least surprises.