Impedance doesnt matter much for a headphone spec, AFAIK. The frequency response is what you want to look at. All of those show good frequency response in theory. However, the numbers quoted dont tell you much because they dont have a +/- indication. Response from 20 Hz (very low frequency) to 20 kHz (very high frequency) is excellent, and in a perfect world response between those two figures would be ruler-flat. However, all speakers and headphones deviate from flat response. Response of 20 Hz-20 kHz +/- 3 dB would be excellent; +/- 10 dB would be rather poor.
But in the end, numbers dont matter as much as how do they sound? You can have headphones with similar response specs that sound very different. Its always best to demo your options and decide for yourself. As an example, a while back I bought some headphones based on the testimonials of several people who affirmed that they sounded great. I was sorely disappointed; I thought they were mediocre at best.
Regards,
Wayne A. Pflughaupt