As I understand it, most average analogs deliver anywhere between 1-3 mg's of nicotine per cigarette, and the nicotine's half-life in your body is around 2 hours.
So, if in a given day of say 12 waking hours, you smoke a pack, then that is (in theory) approximately 24mg's of nicotine over the course of 24 hours.
I imagine that is how both the NRT's(which, in your case would deliver slightly less nicotine than a cigarette an hour over 24 hours) and E-cig's tried to model their systems(where in a perfect world a cart is equal to a pack of cigarettes)....
but beyond that...your individual habits/the cart/the vaporizer/your metabolism and several other things should surely alter how either would effect you.
To make a long post short, there probably isn't any way of accurately saying.
Edit: but for all I know, I could easily have no idea what I'm talking about lol.