24mg is a definite for strength... And ego twist gives ease of use with choice of how much hit you want in your throat and lungs... As far as im concerned, i just started using rebuildables and will use nothing else anymore... Its worth dealing with them for the flavor throat hit and quality of vapor... If not using genesis or rebuildable attys, a good carto, preferably lower resistance with some sort of tank is the only way to go.. I was a dedicated smoker at least a pack a day and through this process am at 6mg nicotine strength and vaping less evry day bc of my genesis atomizer