For me it's a toss up between two single coil setups.
My adv is a DoggyStyle rta using 28 gauge ss wire, 3mm ID, 0.34 or 0.44 ohms at 15-16 watts.
I also really like my Ares rta with the same wire and ID, 0.58 ohms at around 18 watts. I keep that one at home as it's a bit on the big side to pocket conveniently and I'm also not as sure it won't leak.