The main reason I've switched entirely to my Achilles RDAs is because "drippers" don't have any of the "vacuum" issues that can cause all kinds of problems, from dry hits to leaking to flooding ejuice into your mouth. Also, being able to top-fill without removing the atty from the mod is wonderful.
A lot of folks maintain that a dripper offers the best flavor, but I was very happy with the flavor from my Kayfuns, I just got sick of those vacuum issues (though they're a lot less bothersome in Kayfuns than in most other tanks) and having to take it off the mod and fiddle with a tiny screw everytime I needed to refill. Also, my all day/everyday vape is a massive gunker, and in a tank that holds a lot, that kind of huge gunking problem can cause a LOT of juice wastage. If the juice at the bottom of the well in my Achilles turns dark, I waste only a few drops, maybe .5ml at most, rather than 1-3ml.
There are RDAs that hold a good bit, so you don't have to drip everytime you turn around -- the Achilles is a good example; it holds 2.5ml, same as the small kanger T3S's I started with -- it takes me quite a few hours to vape it dry. Some RDAs have serious leaking issues -- Magma! But the Achilles is threaded, with o-rings backing up the threads, and with its design, it NEVER leaks -- NEVER. It is a very tight draw, even with the airflow screw removed, so if you like anything other than a tight MtL draw, you wouldn't like it.
Andria