Give the larger capacity a defined task
List the items that justify 40 liters and consider their weight as well as their bulk. If the bag is intended as a destination extra, check how often it will actually be full. The title does not establish a frame, hipbelt or laptop compartment, so those features cannot be assumed when planning the load.
Compare the bag before and after packing
Request a measured folded footprint and a clear demonstration of how it returns to that form. In its open configuration, inspect the straps, opening and available pocket arrangement. Ask for the empty weight if compactness is the main reason for buying. The supplied title does not make a weather-protection claim or identify a care method.