Hi Simerese. For me the micro coil gives the absolute best flavor for the amount of time invested in making it. Basically I can take a 1/16 drill bit and wrap a 10 wrap coil, thread it with cotton and go on about my day in less than 4 minutes. I could probably get a more flavorful vape from some other build, but right now, it's my goto coil and it's giving me an excellent consistent
vaping experience.
There are many theories as to why the micro coil gives great flavor. Most seem to think it is because there is more wire to vaporize the
juice faster and hotter, producing a clean vape where all the liquid components are vaporized at almost the same time. There are posters here with much more expertise than I about micro coils (superxdrifter being one - the grand-daddy and probably the first micro coil builder in these parts)
You can read all about difference micro coil builds
http://www.e-cigarette-forum.com/forum/reos-mods/446263-micro-coils-ohms-description-12.html <--- there.
As for the size of the internal diameter of the coil, well that kind of defines if you are building a micro or a nano. Again, it all seems to boil down to wire surface area and wicking. With most nano coils, you'll have to put the cotton around the coil and not through it. I've had mixed results using this type of build, although some use it all the time and say it is better (provides a faster response and more flavor) than a micro build.
It's a whole new world out there, just keep doing what you are doing, reading, learning and watching others build on you tube. Rip Tripper has some pretty good building vids if you are interested.