there are alot of articles written in this forums about your inquiry. in my personal experience, the only advantage of automatic batteries is that you vape like how you smoke-- inhale on the device, exhale, that simple. That is the ONLY advantage of automatics.
In terms of battery life, manual batteries are superior since you have full control of battery activation through its button switch. Ive had automatic batteries that ignite by itself for no apparent reason FOREVER until it dies. I've read that some automatic models even have movement-based sensors that ignite when you are simply walking with it in your pocket... *_*
In terms of actual battery lifespan, meaning the hardware itself, manual batteries are also superior due to the fact that the battery is sealed where the atomizer connector is. I actually started out with automatic batteries c/0 a poorly made and cheap chinese e-cigarette unknown brand /model that had a lifespan of about
a week per battery. I figured that the main reason for this was probably because of all the juice that trickles down to the battery that has a hole in the middle where the inhale sensors probably are whenever i drip and vape. Later did I know that i wasnt supposed to drip in the first place (my vendor insisted otherwise).
In terms of vaping experience, I can 100% say that manual batteries are far superior than autos. They never misfire, the amount of vapor is thicker, and it is way easier to inhale --
autos require more inhaling to activate the sensors and in time gives me ridiculous stress on the neck area over time.
In summary, with the devices that are out market right now, all i can really say is that autos are stupid, manuals are the way to go. Hope this answers your question