For me important thing is convenience. So when I decided to move from rebuilding of protank coils to RTA I bought Taifun GT2 and kayfun V4. Rather happy with them. But for convinience new subohm tanks (like subtank) are even better - they have a choice of screwing in prebuilt coil on the go, when there is no time/tools/place to rebuild. I am waiting for something like this appear for tootle puffers. I'll buy one.