Is a duffel bag or rolling duffel better for travel?

It depends on how far you walk with your bag. Specialist communities note that wheeled duffels are easier on the body in airports and hotels but eat into capacity (wheels and a handle frame add weight) and struggle on cobblestones or stairs. Soft duffels with backpack straps, like the Patagonia Mini MLC, are far more versatile but uncomfortable for long hauls when fully loaded.