Traditional seating, with the advantages of a more open hip angle due to the sloping seat.
Sitting on an Ergo shape, the angle between your upper body and thigh (this is the hip angle) will be at least 110 degrees, so that your pelvis is tilted forward. Tilting your pelvis in this way means your spine retains most of the natural S-shape.
The Ergo shape design prevents pinching in the upper legs.