I'd have to say the Velocity. I've been trying out a load of RDAs at a local shop but still haven't found anything to beat it. It's two post but has 4 holes. I've built single, double and quad coils on it, can have airflow as tight as a ciggy up to full lung draw open and has a wide bore tip as well as compatibility with small drip tips for flavour. I'd love a new shiny RDA but I haven't tried one that performs as well or as versatile yet.