The best
rda for flavor I have came across so far is the gas
mods gr1. Next on my list for flavor is nudge, and then the entheon. All of these are single coil with slightly restricted direct to lung airflow (nudge does have an airy and restricted top cap included, and the gr1 has different airflow attachments included to restrict or open up the airflow to your liking). If you want more open airflow the wasp nano is hard to beat, and I hear the recurve is great in the flavor department.
