definitely the nicotine, possibly the voltage, maybe even both. everyone smokes cigarettes differently. i don think it matters which brand, how often, or how many cigarettes you smoked. i think the bigger deciding factor on determining appropriate vapor setup is HOW you smoked. i for one took deep drags. i constantly craved the th )although i had no idea it even had a name when i smoked). i got to a point where i would steep my cigs! at the time i jokingly called it aging. but what the end result was, was a harsher draw. once the freshness of the cig evaporated, they would become much better to me. i never packed them, in fact i often loosened them up (especially once the "fire safe" cigarretes replaced the "normal" ones). however, i only smoked about 5-8 cigs a day.
so, all in all, its all about how you smoked. if you puffed lightly and daintily, your gonna want like 3.7v and lower. if you took decent sized drags, maybe more voltage and more than low nicotine. deep drags, and th fanatics high mg, higher than normal voltage. but as always, YMMV.
..and she was disgusted): She said it burned her throat and lungs and that her lungs felt heavy. I'm smoking 24mg juice and she doesn't smoke as much as I used to smoke. Since I quit analogs she only smokes about 7 cigs a day now. Could it be that the nicotine was too strong? I know it wasn't the cart cause I took a drag after she did and it was fine and didn't burn. Please help I don't want BT and BP to win over her. I want her to feel like I now do and want for her to open her mind to this great alternative!