Rebuildable tanks are available with either a single or dual-coil build deck & most (but not all) dual coil RTAs are suitable for use with either one or two coils.

For most users, a single coil setup will likely be perfectly satisfactory, this is what I use for 99% of my own exploring. It's simpler to set up with only one coil/wick, and likely the most efficient option for juice consumption overall, especially when the wick-resident juice is taken into account.  Nevertheless, it remains impossible to deny the advantages of a good dual coil setup, which can really take things to the next level for those who are ready. So assuming we have the choice - what factors might influence our decision?

Reasons For Choosing a Dual Coil Rather Than A Single Coil Setup

• Increased Wattage/Potency Two coils provides a much greater safe max Wattage capability and (if used), far greater single-toke potency when compared to an otherwise identical single-coil setup. As explained in the tank buyer's glossary, most users find a single coil to be perfectly adequate in DTL "sub ohm" tanks

• Vapour Smoothness When properly using the additional Wattage/Potency of a dual coil setup, many will find the vapour to be unexpectedly & deceptively smooth. Although initially a pleasant surprise, such vapour can often pack an unforeseen & staggering punch, catching even experienced trippers off-guard.  Therefore, caution is very strongly advised.

• Wider Wire & Coil Choice For single coil setups, the coil heating surface area is always a top consideration, with choices often restricted by the build deck's terminal gap, & coil diameter limits. However, on a dual-coil deck, options can be far wider. For a dual coil DTL installation, I'd suggest starting with two coils with 5 turns of 26x2+36, inner Ø 3mm.  However, I've had excellent results from dual finer MTL claptons like 30x2+38.  Feel free to experiment around, and suggest staying within the max wattage guidelines given by Wirebuddy  - Note that wirebuddy gives max Wattage per coil so simply double up for two.

• Greater Juice Strength Versatility Dual coil operation opens up many more options for using weaker juice strengths, because a lot more potency can be achieved from weaker mixes than would otherwise be the case with a single coil setup.
  My own usual de-facto starting mix for single coil DTL setups is approx 1:4 60PG/40VG (see Juice Buddy). This juice can also be brilliant in dual coil setups, although many find that weaker juices (e.g. a 1:5 or 1:6) can also work well depending on the coils/Wattage used.  However, there's often so much Wattage headroom and excess of punch, the exact juice strength becomes less important.

• Juice Consumption Unless the extra wattage/punch endowed by the dual coil setup is used, then it'll generally be more juice-efficient to use a single coil setup. Coils require a certain minimum Wattage to generate vapour at the optimum temperature/concentration for efficiency, so for most users it's generally preferable to have the Wattage dissipated by just one coil rather than split across two

• Toke Rate As well as a higher Wattage setting, dual coils appear to require a stronger toke than single coil setups to obtain optimum performance.  Insufficient toke rate when upgrading from single to a dual-coil setup is a common mistake, which inevitably brings disappointing and sometimes unpleasant results.