And those two sheets and compare - especially look at:
- FREQUENCY RESPONSE (no peak around 3.5khz with 600ohm version suggesting a little bit smoother sound in that department = highs)
- 30HZ SQUARE WAVE (significantly more square-like look of 600ohm version suggesting a littel bit tighter bass)
- 300HZ SQUARE WAVE (reduced ringing with 600ohm version suggesting a bit smoother and precise sound overall, could image a bit better)
- %THD+noise (significantly lower with no significant inconsistencies with 600ohm suggesting cleaner sound overall)
- IMPULSE RESPONSE (let's say they are the same so both will be equally "fast")
Those differences will be definitely small but expect a bit cleaner and tighter bass response along with cleaner and smoother highs... A LITTLE BIT, not much!
Depends on how much you want to spend... But 600ohm version is better, definitely. Drivers seem to be better controlled, simply.