The DT 700 PRO X is essentially the same headset but with a closed-back design instead. If you want the option to listen to your music on the go, this is a better option than the DT 900 PRO X. Both headsets cost the same, but the open-back version has a better midrange response for mixing, though the treble peaks are greater than the DT 700 PRO X. You can see a frequency response chart comparing the two headsets here.