A gym bag that lives on a train needs different qualities from one that lives in a car boot. I have carried more than thirty of them on my commute, and three things separate the keepers.
Compartments that matter
A separate shoe pocket is the headline feature. A padded sleeve comes next if your laptop travels with you.
Carry comfort
Check the strap width and how the weight sits at full load, not empty in the shop. A duffle with a removable, padded strap works for most people. Longer walks favour a backpack.
Materials
Coated fabrics wipe clean. Look for bar-tacked stress points at the strap anchors, because that is where cheap bags fail first.
Separate shoe compartment is the one feature I will not give up.
The Joust Duffle has been on my shoulder for two years now and it still looks new.