I have both the Drop DCA Closed X and the Noire. The Closed X completely re-educated my ears with regard to headphone bass reproduction, because, for example, my dynamic-driver HD-650's sound just unacceptable to me now because of the obvious and audible bass resonances associated with that driver in comparison to the planars. And the weak-ish sub-bass of the HD 650 does not gracefully accept EQ to get it to Harman levels or something close to it, while my two DCA 'phones EQ smoothly.
My point is that the planar difference is not just in the measurements, but is clearly audible, at least for low-distortion planars like DCA's. Dan Clark has said many times, however, that we are collectively so used to bass resonances arising from almost-omnipresent dynamic drivers or from room effects and speaker enclosures, that we come to expect them and some of us may prefer them. Personally, I find the better separation, and tight high fidelity of low distortion planar bass to be preferable. YMMV.
Pick your poison, low-efficiency or low-distortion, but there is a payback for accepting the low efficiency of DCA planars if you do happen to like the sound. That said, I also have a Sundara, another planar that I like, and it is a lot more efficient than the DCA headphones, if also heavier and less comfortable. But the Noire is my #1 pick out of the three, and I had to make sure my amplification was adequate only once, when I bought the 'phones, so not much practical effect from the higher current demand.