Worth keeping in mind here that the lower the impedance, the more efficient headphones are in converting the incoming electrical energy into sound. On the contrary, the higher the impedance, the more electrical energy is required to drive the headsets tiny speakers.
The 150 Ohm is a typo or mistake afaik. To the best of my knowledge there has only been a 120 Ohm version and a 50 Ohm version. The 120 Ohm version production stopped a couple years ago (apparently due to fire at the factory) and since then everything has been 50 Ohm. Generally the lower the impedance the easier to drive but this, like everything else, has exceptions. In this case though it should hold true.