also thinking about this
510 U-DCTank Combo
it has a 6ml
tank but it uses cartridge cartomizers and it locks them into place
but the protanks use a coil head
so what is better in terms of lasting longer and better hits using a normal cartridge cartomizer or using the coil heads in the protank series.
cartridges are use and toss.
Atomizers for clearos are use and maybe toss; you can clean them, or rewick them; or maybe even recoil them if you got good eyes.
cartomizers also use a filler stuff material inside that acts like a big fat wick; the taste of the carto is going to depend alot on this material.
The great thing about cartos is that it boils down to having a standard atomizer that will work with different manufacturer
tanks; and if you don't like one manufacturers carto you can just buy another brand.
You can find lots of videos on rebuilding clearo coil heads
a miniprotank2 is an excellent start; eGo thread; decent airflow; easy to find coils; can be rebuild if you are interested; can change driptip.
I'd consider a carto system to be somewhat of an upgrade of the standard clearo; but you have to know how to prime the carto; you have to be prepared to keep buying replacement cartos; you'll probably be needing some tools that make cartos convenient to change etc; having said all that, I do not actually use cartos myself; to rebuild a carto, you'd need a special atomizer called the Sophia; the only example of a rebuildable atomizer designed to fit in a carto tank.