I just bought a mayflower Objective2 Rear Power – Bamboo Headphone Amplifiers and the current headphone that I'm using as a daily driver are beyerdynamic.DT 770 80 ohms and plain a upgrade to the DT880 250 or the DT880 600ohms, So i done lil bit of research i find that 600 ohms as lil more bass too it
I've tried looking into this myself. I found out, that the sonic differences are probably minimal, so I went with the 250 ohms, as they can be driven okay on other sources than your main headphone amplifier.
But note that almost all camparisons vary a bit in the perceived differences in sound! If you really want the one best suited for you, the only good way is to find an outlet that sells both, bring your amplifier, and do a side-by-side comparison.