I was curious when Iffy said that.....now you...... I was under the impression that VW basically just meant that it would choose which voltage to vape at, but why is it better exactly than vw? (If you can splain it without making my hurt, remember who you're talking to)! lol
I think Sloth has class tonight until 9pm. Don't quote me on that. Unless his students have done him in, he should be here later.
Yes, I had class until 9PM tonight
Then, I had to eat dinner and relax for a while. You all have been busy bees in my absence!
Here's how I think about. Watts means power, and power means heat. Higher Watts -> more heat, lower Watts -> less heat. That total heat can be jammed down into a small really hot point, or spread out over a large warm area, but it's the same total heat. If you have a small, really hot point, that will burn the juice more easily. The same amount of heat spread over a larger area of juice will warm the juice rather than burning it. Somewhere between there, the juice is hot enough to vaporize without being so hot that it burns. That's the best temperature to vape at. You can see that different coils and different attys will focus the heat differently. A little tiny coil without much wick will be too hot at say 20W, while a really big coil or two might be perfect at 50W. It all depends on how well the heat is spread out over the wick, and how well the wick stays wet when the juice starts boiling off of it.
Then, there's airflow. The more air you move past the coil, the more heat is blown off the coil, and the cooler the coil stays. An atty with a tight draw and not much air flow will have a hotter coil, so will require a lower wattage. An atty with a lot of air flow can take higher wattage (and might require higher wattage to get warm enough to produce a decent amount of vapor).
So, now I hope you understand Watts and their relationship to temperature, and why different attys and vaping styles might require different wattages to produce just the right vapor. A VW mod has electronic circuitry that allows you to set a particular wattage, so that you can dial in exactly the right amount of heat for your particular build, atty, and juice. It will take some experimentation to find that perfect wattage.
Here's the tricky part - for a given coil with a given resistance, a particular voltage applied to the coil will always produce the same wattage. If you raise the voltage, the wattage goes up and if you lower the voltage, the wattage goes down. Basically, if you tell me the resistance of the coil, and the amount of wattage you want to produce, I can always tell you the exact voltage you need to make that happen. The opposite is true as well. If you tell me the resistance of the coil, and how many volts you are running through the coil, I can always tell you the exact wattage. So, for a particular atty with a particular coil, there is absolutely no difference between picking the voltage and picking the wattage. A fixed voltage will always produce a fixed wattage for that coil, and a fixed wattage will always require a fixed voltage for that coil. So, in that sense, there's really no difference between VV and VW. However, for most people, it's easier and more convenient to specify the wattage, because that's more directly related to the heat that's being produced. Also, a different coil will require a different voltage to produce the same wattage, and since most people usually vape around the same Watt range most of the time, you can set it and forget it with a VW device, but you have to change the voltage every time the coil or atty change with a VV device (remember, it's the Watts that produce heat, and most people want a certain amount of heat). Basically, a VW device automatically compensates for changes in resistance, while a VV device doesn't - you have to do that yourself, which is more work and difficulty for you. But, other than that additional work, the mod is doing pretty much the same thing for a VV device as a VW device, once the settings have been adjusted.
Now I also understand why I vape at a much lower wattage than many folks.......I like a tighter draw with less air flow. More similar to a cig. 
