Rebuilding your own will give you a wider variety in the builds you use. It will also give you dry hits, gurgling, and pleasure/pain when it comes time to rebuild.
The coil is the easy part. I can do 8 wraps around my screwdriver all day and come up with 8 wraps and not 9. The resistance will be real close and with ceramic tweezers I can get a decent looking coil.
Wicking is another matter. I have had an atty with the perfect build in it. Everything was fine and then I replaced my wick and it got dry hits, or gurgled, or both. I thought I use the same amount of cotton and put it in the same place but one wick worked fine and the other was .....
When its right you feel good with the sense of accomplishment. When you can not get it right after 3 trys you feel like you need a cigarette.
I have an Atlantis and you can have it more airy than a kayfun. Vapor production is greater. Flavor, for me, is about the same. Flavor is a personal thing, some people say they can taste new cotton but I can not. The major thing for me will be when the time comes to replace the build. For the Atlantis just screw out the old and in with the new head. For my rebuildables get out the cotton and prepare for a little work.
Heads cost more than Kanthal and cotton but my time is worth something too. Even If I get the cotton right the first time all the time it still takes longer to wick than screw in a head.
It is easier to fill with juice than a kayfun, a good thing because those big clouds take big juice. I have one that I filled the fill port with aquarium sealer cause it would not stop leaking. I go through the take the top off, fill it, just catch the threads, turn it over and cover the airholes, screw the top on, blow out the juice that leaked. With the atlantis turn it over, unscrew it, fill it, screw it back on, vape. Don't even think about touching your build without getting juice all over.
The first couple of times building is fun but now I find myself with a bunch of stuff that needs new wicks, filling, etc. and I do not want to mess with them.
I have one Atlantis and after a few weeks of living with it I will decide how it is for me. I probably will have some stuff to build lying around but on those nights when the first 2 builds do not work I will probably skip the third and screw in a new head on an atlantis.