Here's my understanding:
The Kick 2 can buck voltage better than a DNA. According to the Evolv website it can buck voltage down to 2 volts.
I.E. If you put something like a 0.6 ohm atty on a Kick 2, then set it to 15w...it'll buck voltage down to something like 2.5v (give or take a little). With a sub-ohm atty like this on a Kick 2, your lowest output possible would be around 7 Watts, while with a DNA the same atty's lowest setting would be MUCH higher (I'm guessing around 29 watts at 7 amps on a freshly charged battery).
The DNA 20/30D models can give more power, it's excellent and highly efficient at 'boosting' voltage, but it doesn't 'buck' voltage as well as the Kick 2. I.E. if you put that same 0.6 Ohm atty on a DNA mod, its lowest setting would depend on the charge of the battery. With that in mind, you'd avoid low resistance atties if you want to get the 'full range' of possible adjustments. I.E. If you wanted to get a 7w vape (lowest it will go?) from a DNA on fresh battery, you'd NEED an atty of 2.52 Ohm or higher resistance.
So, if you like settings below 15 watts and primarily run single coil atties, don't use Sub-Ohm coils on either device. With a DNA you'd probably want 2.5 - 3 Ohm builds or higher to enjoy settings under 10 watts. With a Kick 2, you could still use atties from 1 - 2 Ohms and get the full 5-15 watt range.
For single coil rigs under 15 watts...Kick 2 with a coil from 1 - 2.5 Ohms is probably the way to go.
If you're wanting to drive multiple coil rigs, or otherwise know you'll rarely if ever want to go below 10 watts, a DNA is far more efficient and better for the job.