Vibration versus kneading versus percussion
Kneading rollers, like those in shiatsu cushions, push tissue around in circles — pleasant, but bulky and fixed to a chair. Percussion, as used by massage guns, strikes deeply and rapidly, which is powerful but needs a hand and careful aim.
Vibration sits between the two: broad, even, low-effort movement across a whole area. It is the only one of the three that can be delivered from a slim wearable while you carry on with your day, which is precisely why it works for daily use.

