If you were asking 8 ohms vs 300 ohms output impedance there would be a slight increase in distortion at higher volume at the 300 ohms setting vs the 8 ohm setting, and probably a sense of fuller bass at the 300 ohm setting. With 300 ohm cans the difference between 8 ohms and 32 ohms output impedance will be pretty tiny with respect to perceived distortion levels. But where the 8 ohm setting will shine is in having a better S/N ratio and a more quiet noise floor for a given listening level compared to the 32 ohm setting.
