In short, this.
Elear pads on the Utopia really add a lot of heft to the bass.
Utopia pads on the Elear tone back the bass to a more balanced signature, which is nice, but it also brightens up the treble just a bit...
Thanks Stillhart for looking into this.
This pretty much confirms what I suspected.
It looks like the voicing of the Elear and the Utopia is mainly tied to their respective earpads. This now gives owners an easy way to experiment with their tuning without having to do any serious modding.