I think that flexibility is what is keeping this tank relevant.
You can genuinely hard set the airflow in to your preferences.
With airflow control you tend to just adjust the speed in which the airflow runs over your coil but with the dvarw you can find and set what works for you. The rest you instinctively do with your draw style.
Funny I had to reduce the airflow size on the strike the other day too, just to match the dvarw.
It forces you to spend some time with the airflow choices due to being a pain to change (compared to an airflow ring). So you get to find the finer nuances within that airflow.
Very good indeed.