What I would like to know if the 1.8ml if they perform the same results of vaping out exhale/inhale of vapor as the dual coil. Or the dual coils are the one thats does better?
That depends. I use dual coils and single coils. I prefer my 1.5 ohm dual coils with most juices above 4.3 load volts. With some juices, I like them at 5.0v and even 6.0v, others as low as 4.3 or 4.4.
A single coil doesn't have the ability to perform at that wide of a range of voltage. - A 1.7 ohm single coil does really well at 3.3 to 3.5 load volts for me -- A 2.0 ohm single coil performs well from 3.9 to 4.3 load volts --- a 2.5 I'll use around 4.5 load volts -- a 3.0 ohm around 5.0v.
It also very much depends on the juice.
My suggestion is to try the dual coils and the single coils and see which you prefer with your juice and at whatever voltage your PV can create.