I use 14500 mods almost exclusively so I stick with RDAs that are 17mm and under. My two favorites are the eBaron Dripper by Leo and the Kayfun Mini v2.1 ES.
The eBaron Dripper by Leo comes in two versions: the Dripper Spiral and the Dripper Pro. The former has a spiral design on the drip shield and the latter has a plain drip shield; the Dripper Pro has a wider base that matches the tapering and finish of the Provari. Internally they are identical, so any review you see for one will apply to the other, performance-wise. They use ceramic cups and are meant to be set up with R/NR wire, though it seems a lot of people are unaware of this or choose to ignore it and set them up without joining the NR wire. They hold a lot of juice for a dripper that size and I like them enough that I have three of them, two Spirals and a Pro, in my regular rotation. The only thing I don't like about them is that they do not have an adjustable center post.
The Kayfun Mini v2.1 ES is sealed at the bottom so it can't be used as a bottom-feeder. It's also quite expensive, especially when compared to single-function drippers. If neither of those things are deal-breakers for you, it deserves a look because it's superbly crafted, extremely versatile, and a great vape. If you want all the details, see the user manual. You can use it in drip mode, tank mode, or long tank mode depending on how much capacity you want. Everything's adjustable. Super easy to set up; plain old Kanthal & silica will do ya. Svoe Mesto also makes a cool thing called the Sticker that lets you mount your Kayfun Mini side-by-side with a small mod if you want a different form factor. The larger Kayfun v3.1 ES has no drip mode, in case you were wondering.
I'd like to try the Cyclone sometime. It has a nice look to it (IMO) and appears to be high quality. I think a couple of my local brick & mortars carry it, which is always nice.