The best, simplist explanation on what resistance/ohm to use for your particular
device's voltage output is in this article. It was written by the guy who created the safe
vaping power chart. It is meant to be used only as a general guideline.
Guide to Safe Vaping - E-Cigarette Safety | Ecig Advanced Community Blog
According to the article and the chart, any ohm between 1.5 and 3.0 ohm is fine to use, which one will provide you with the best vaping experience will be subjective and to your own preference.
I will say from personal experience, that dual coils do drain batteries faster, and I never noticed any benefit garnered from using a dual coil to warner using one. I switched from dual coils to single coils and found them to be much smoother. I say try some single coils out and see if you prefer one over the other.