How is this better than a massage? After a massage I feel relief for a couple of hours and that's it.

You've described the main difference exactly. A massage mostly works on the symptom - it eases muscle tone, and the effect doesn't last long. The hang, on the other hand, removes the very cause for many people: the spine is compressed all day (laptop, scooter, sitting), and here it's lengthened under your weight instead, the joints are given space, and the body 're-learns' the habit of moving more evenly. The feeling is close to a deep massage and relaxation, but the cause goes deeper. Many combine the two - they get along nicely.