it´s not only the ohm factor!!
different headphones have different sensitivitys. for example, for tracking in use a cheap superlux with 32ohm and a sensitivity of 98db spl. with my cheap akg´s k44 k77 also 32ohm but a sensitivity of 112db spl is more twice times louder.
if you work with very dynamic singers, or accoustic instruments, the main level has to be quiet low, so a better, but more energy hungry headphone would´n do the job. so it really depents on what are you doing. for mixing it´s ok. for me, but it´s nice to have a bit more headroom.
but most other brands seems to have more power i their headphone amps.