My opinion is in the form of a question:
How long is a rope?
Nicotine from vaping enters the bloodstream differently (Mouth and sinus mostly), is slower to hit you, doesn't have all the fancy chemicals to shred lung (surface area ftw!) and increase nic intake. Vapers all seem to pull differently. When I direct drip I get 2 good hits till it starts going acrid, my wife easily get 5-6. I inhale (most, not all is through mouth/sinus), she doesn't.
I was 1PAD and went 100% vaping @18mg 30 minutes after it arrived, though I chain through the work day. Some folks here are 1/2PAD and need 24mg while chaining. We all seem to have different needs regardless of our original smoking habit.
I haven't attempted to maths 1 vape = x drags since I don't feel they are comparable. Cigs are specially designed to get you hooked faster and deliver as much nicotine as possible (BT says it's to improve flavour....om nom nom benzene is tasty!). Vaping seems more geared towards dealing with cravings more than causing them.