Dripping probably gives the bets flavor -- your atty permitting, of course -- but I've the SmokTek duals come pretty close. But I've never been fond of dripping so cartos also satisfy my need for convenience and low maintenance. But the thing with variable voltage mods for me is that over time, even with cleaning, atomizers can get stuff fused to the coil that's extremely difficult if not impossible to get off. This raises the atty's resistance. With fixed voltage mods you're stuck with whatever performance that leaves you with. With multi-voltage mods that gives you a couple more options but it might not be granular enough to give you the performance you want -- it may either be too cool or too hot. With VV I can tune the voltage to max the resistance so that the performance is always the best I can get it regardless of the atty's resistance. It still won't make attys and cartos live forever but it can extend their functional lifespan. Plus, the advantage of dual coils is that the coils share the workload. In a 1.6ohm atty you've got twocoils in series at 3.2ohms, so each coil does half the work, which makes them last longer.
Voltage is only one part of battery size though, and a small part; most AAA-sized or larger batteries are 3.7V. Capacity is the big thing; the more capacity, the bigger the battery. The ProVari uses an 18500, or can take an 18650 with the extender cap. (Unprotected AW IMR 18650s fit perfectly. Protected 18650s fit but leave about a 1/2mm gap in the end cap when you tighten it down. Provape will have a little shim you can install to take care of that once they release their branded 18650 batteries.) Despite that though the Provari actually feels good in the hands. Heavy, but good and solid and not overly big.