If I were to start out over again I would only consider a Joye 510 ( and a ego for the long battery life) or a DSE901 ( and a DSE905 for the long battery life). I have tried Greensmoke, Bloog, and Vapor king but found that I enjoyed the vapor and throat hit of the DSE901 to my liking. I vape 18 mg and mix my juice with 30% VG, as I have found that full PG is a bit of a sinus irritant for me.
If you go with either, spend a few minutes reviewing the cart mods as the straw method works great and lets you put almost double the juice in the cart. The battery life on the DSE901 auto batteries, for me, is about 4 hours with a recharge of about 1 1/2 to 2 hours. With my DSE905 I can go 12 hours between batteries and vape like a banshee. The vapor quantity is only slightly increased with the DSE905 but you got to love the battery life. I still keep to 3.7 v and HR atomizers as I have heard that if you start vaping at higher voltage it is hard to go back to 3.7 V. There are probably some who will argue this, but that's my personal opinion.
Good luck with your purchase.