So the fatter and tighter the coil, the more it vaporizes the juice?
It's more complex than that.
Think of the coil in terms of how much wick it covers. Take two coils with the same inside diameter of 2.5mm, one is 5mm wide the other 10mm wide. Lets say the 5mm wide coil can produce 20 watts of heat at 180mW/mm and evaporate the eliquid optimally. Now take the 10mm wide coil, which has twice the surface area and make it produce 20 watts of heat, you will get 90mW/mm^2 of surface area. So with the wider coil you need to use twice the power(40W) to hit the same surface temperature or 180mW/mm^2.
Now assuming the wicking can keep up, you will evaporate twice the eliquid with the 10mm wide coil at twice the power.
Now with Clapton coils you get a bit more surface area with the same width. Not as much as most people think you do because the liquid that capillary action draws into the nooks and crannies is vaporized within the first second, after that the difference is minimal. Now if you are only taking a one second puff that would matter.
The cost of this slight increase in surface area is thermal mass. The wrap wire does not conduct much current at all so it is only acting as a heat-sink for the wire it is wrapped around. This causes the heat-up time to slow down dramatically unless a lot of power is applied.
This is basically two ways to achieve the same goal. Make the coil wider or for short fast bursts wrap it in small wire.
Making the wick wider is more efficient but once you wrap a coil that is as wide as the air slot the only way to gain surface area is to wrap it in small wire.
Also contrary to popular belief, wrapping a 10mm wide coil with 28awg will have more coil to wick contact than a 10mm wide coil made with 22awg wire.
