Dual coil cartomizers' design is intended to produce more vapor. Two coils - twice the vapor production, right? In reality, I've not found that to be true.
A dual coil 1.5 ohm cartomizer in reality is the same as a 3.0 ohm single coil because of the way ohm's law works.
I switched from dual coils originally to single coils because in my experience the single coils provided a smoother vape and were less demanding upon battery life. The singles make just as much vapor. As I said before, to get the full benefit of dual coils, you need to power them with over 4.5 volts of power. A standard eGo battery only puts out 3.5 volts or less of power, and even the Spinner and Twist eGo's that are variable voltage will have a hard time providing that over time. Dual coils are best suited for more powerful batteries found in larger PV's that use the replaceable batteries.
To get more vapor from a single coil cartomizer in a fixed voltage eGo, use a low resistance cartomizer (1.5 - 1.9 ohm) and use an e-liquid with a higher percentage of VG than PG ratio.