RDAs and RTAs both feature “Rebuildable” heating coils, which is what the “R” stands for. In RDA, the “D” stands for “Drip”, and the “T” in RTA stands for “Tank”.
Both require that you install coil wiring and wicking material (usually organic cotton) yourself, either by actually coiling your own resistance heating wire, or by buying pre-built wire coils, and then configuring them in the RDA/RTA deck.
RDAs (Drippers) require manually dripping liquid onto the coil after every couple of hits.
RTAs (Tanks) have a liquid “tank” (reservoir) that sits atop the coil, which automatically feeds liquid onto the coil and allows the user to go through several millimeters of liquid before being required to refill.
To complicate matters, Squonk RDAs, which are paired with Squonk Boxes, feature an RDA with a liquid channel running up from underneath. Squonk RDAs are fed by a manually squeezable liquid reservoir that resides within the mod box (power brick) itself. The user squeezes the reservoir to wet the coil as needed.
Which is better? That’s mostly a matter of preference.
Types of vape tanks
RTAs are certainly the most convenient to vape on, in theory anyway: They feed liquid automatically as needed. However, this added convenience comes at the expense of added complexity of the device’s internals: There is more that can go wrong, the airflow channeling scheme can be more complex, and the coil build area — as well as the wicking area — may be smaller (or the overall device may need to be bigger).
To expand on that last point, the space you have to build your coils and wicks in an RTA tends to be more constrained, primarily because that space now needs to be shared with liquid storage. RTAs usually have an additional internal “hood” that closes over the entire coil build area to isolate that area from the liquid storage — whereas in an RDA, the entire diameter of the RDA device can be utilized as coil/wick real-estate.
“Squonk” systems are an attractive alternative, as they don’t have the RTA size constraints. They do introduce a unique new hardware requirement though: Your mod — the power brick, which normally only houses your electronics and batteries, and is normally interchangeable with most coil systems — needs to be built specifically for squonking. This means it must house an integrated liquid bottle with a tube fed through its top, and a partially-exposed method of manually squeezing that bottle to wet the coil. The bottle itself takes up space that would normally be used for an additional battery, so you’ll need to either settle for less power or lug around a larger, heavier mod box.
Purists will stick with RDAs for their simplicity. There are no additional mechanics to get in the way or worry about: You need only focus on meticulously building your coil, with no shortage of raw power, and without getting sidetracked by other concerns. Coils are the most important part of the vaping experience, as they, more than anything else, determine performance, flavor, vapor production, etc. For many enthusiasts, coil building is practically an art form, and they may not want to waste time and energy worrying about anything else.
I would not say these 2 are better than the other, depending on the design the RTA which I’d use if I’m out and about and not have to worry about carrying extra juice where as the RDA I have to carry juice, hence I own both types I use my RDA more because I’m out and about less.
Depending on your activity, that if you know that you’re in a hazardous environment I use the RDA which I don’t have to worry about the glass been knocked around and been damaged, if I’m not in a hazardous environment I use the RTA.
I also use the RDA to try and test different flavor profiles, which I don’t have to worry about unscrewing the tank system of the RTA to do so.
In the world of vaping there are very few things that can be considered “better”. Especially when comparing different types of devices or atomizer, different styles of vaping, different eliquids, this is all a matter of preference. Different people like different things. Whatever is best for you may not be the best for the next person.
Others have done a good job explaining the differences and pros and cons of RTAs and RDAs so I’m not going to get into that. The most important thing in finding your perfect vape setup is to determine what is best for you. Learn about different types of devices, try out different things when you have the opportunity. No one’s opinion on what they prefer is more valuable than your own.