I have all three.. The theorem, avocado 24 and serpent mini. The theorem and avocado is more alike compared to the serpent mini being genesis typed
tanks and has really high airflow. The Serpent mini is a conventional RTA but has a much bigger build deck allowing for even clapton
coils up to 3mm diameter or maybe more, the serpent mini would be more for a restricted lung hit or mouth to lung, the flavor is pretty great. The avocado 24 would be the best in terms of flavor out of the three IMHO, if you have a single batt mod and don't wish to use bigger gauge coils, the serpent mini would be your best bet. If you plan to do double instagram worthy coils then the avocado 24 would be perfect. The theorem is kinda a middle ground in terms of size and flavor between the avocado 24 and serpent mini. I think all three are good, really depends on what you are looking for.