The aerotank isn't designed to be rebuildable (although people have figured out how to do it anyway). Much like the protank, nautilus, and other clearomizers, it takes replaceable coil cartridges. In my opinion, it's the best of this breed, but none of them are going to hold a candle to a true rebuildable
tank like they KFL+.
With an aero (or other clearo
tank) you're making a trade-off - you get ease of use with the changeable coils cartridges, but you trade it for flavor, usable power range, and cost (coils are $10 for 5 versus a $6 roll of wire and $2 box of cotton balls that will last months to years).
It really depends on what you're after. If you're not intimidated by building coils, go with the KFL+ or Russian to start with. Once you've got some time with it and a feel for what you like, you'll know if you're interested in a dual coil
tank (Aqua, Fogger, etc) or if you'd like to try the Squape's configuration, or if you're happy with what you have. If, on the other hand, you have no interest in rebuilding, then the Aerotank is an excellent choice.