Thanks for the measurements.
Although there are measurable differences between both units, I don't see the Dragonfly as having "bad" performance. -72dB SINAD, 0.03% THD (and primarily 3HD at that) and -125dB noise are not "supposed to be" audible values. Whether the difference in output voltage is an issue, with an individual's choice of headphone (1.2V is fine for line level) it may be irrelevant as well.
To me it seems to come down to the desire for balanced out and your preference for size overall, and there is the power draw to also consider. Oh, that and whether you can decrypt Enigma transmissions ;-)
Speaking of WWI and II, I find it interesting that the Dragonfly and Da3 seem to have a "Cold War" heritage. I'm reminded of a conversation I had with an E8 at [undisclosed] AFB around 1992 or so. A North Korean defector had flown his Mig-25 to Japan a few years earlier. The differences in technology were, amongst others, that "there were exposed rivets on the airframe, something we would never allow" yet "precision high alloy parts of titanium were there where they needed to be" and "the engines were way more powerful than necessary" with a "large fuel capacity" and a "high fuel consumption" with the result that, like all Soviet fighters, top speed was higher than Western equivalents. And then we have the Chinese DAC with sharp corners, large physical size, more than adequate performance and high output power with high power drain.
Regards