Thanks a lot, great answer.Everyone has their preferences. I speak for myself only. An internal airflow such as seen on the kayfun Mini V3 and KFL19 takes up hardly any volume and certainly less parts and complexity versus an external airflow ring like on the Prime or V5. An internal airflow setting requires more effort to set your desired flow vs external but it isn't hard to do. Given the mass of people rarely change their airflow setting, this "set once and forget" internal design simply allows for a more compact atomizer, less complexity, and nothing that comes out of adjustment. For those who like to change airflow frequently (don't know many people like that), then the external airflow adjustment might be a better design for them.
Also, an internal air flow screw allows for a continuous setting. An external system forces you to use one of their pre-factored holes.
i like the idea of simplicity and also the fact that can be smaller. I’d say it would be a great complement of my Prime. I have seen pictures of the KFL 2019 24 mm on the Dani Box Mini, it is a beautiful and a bit brutal looking combo that will be hard for me to resist. 3.5 ml wouldn’t hurt either.
Another thing that i love with the Prime is that there isn’t any liquid below the drip tip once i take it out. And filling it up is a pure joy with the smooth threading.