The three or maybe four top rta's right now are Kayfun, Taifun, Aqua and maybe Fogger v4, though I dont have a fogger v4, I do have the other 3..... I think between the kayfun and taifun, flavor and vapor edge go to taifun.... just my opinion ymmv.
Ease of build probably goes to Kayfun overall... with Taifun being a close second.
The Aqua is a little different animal, better but different too... pretty easy after you get the hang of it, its a small build deck for dual coils, but thats just a learning curve... I also bottom fill which is tricky the first few times, then its as easy to fill as anything else imo... just have to get used to it. it has juice control which is awesome, adjustable air flow control unless its full to the gills

, dual coil which makes juice flavor, nic hit, and vapor more
intense imo ymmv. But will require a little more power to push it properly, but will work fine at 12 to 15 watts no problem.
I use kanthal (various sizes) and organic cotton balls as wick on all three..... going to depend if you want easy to build, easy to fill, or what device...............