There's not much difference, but it's better to do it on a cushion. To achieve the same exercise effect, it is necessary to increase the intensity of exercise on the cushion! This is because the cushion is elastic. When you apply force, your hips will droop, and the pressure between your upper body and the cushion will decrease. The cushion will recover some deformation upward and continue to give your upper body an elasticity. As a result, the strength came down! But doing it on the cushion is very comfortable!