RDAs are preferred by vaping enthusiasts who like to get the full flavor of their juice. The short travel offers a direct hit. They can also have great control over the airflow. Users must drip the liquid onto the coils underneath of which lies a small juice well.
Different types exist so learn more about them to find the best RDA coils. You can get mesh coils or organic cottons for this. There are also staple Clapton coils with single, dual, quad, or eight cores. More cores mean greater surface area for creating awesome flavor. These can also make plenty of clouds.
These are cheap enough that you can experiment with several of them to see what works well for your RDA and your personal vaping style. Look at different demos to see how others are using their coils and what their results are.