If you want a lot of air I'd say Subtank. If that's not as big of a deal then maybe kayfun. I have both, and the subtank is probably the best vape I've personally had. Additionally, I've recently had some issues with wobble on the juice control ring from my kayfun. Having said that, I'm vaping the kayfun right now, and out of all the kayfun's I've owned the v4 has the best draw with the afc screw removed.
To be totally honest I'm looking for a single coil RTA. A kayfun alternative with more air, and I do believe I'll be getting a Lemo here shortly.