I think it depends on
juice and coil type. For me the RM2 and standard Cyclone are very close. So the RM2 wins for cost and ease of build. However the Cyclone + AFC cap is a great dual coil cloud
rba.
The Divo I think has a slight flavor advantage enhancing the sweeter or higher notes.
The Igo-S from Rob is a great little RBA and clear bang for the buck leader.
The Chalice also has this sweeter note advantage and the center drain hole, but is 4 times the cost. I like it a lot and just ordered another one. So 3 of my mods will have Chalices, 3 will have RM2, 1 with Divo, 1 with Cyclone + AFC, 1 with Igo-S.