Given the choice of technologies, I'd like to have a VT device ... Variable Temperature. That's not going to happen except in a proprietary device that requires the use of atomizers with a built-in thermistor to sense the temperature in the bowl. Even then, different juices will like different temperatures.
I'm happy with the variable voltage of my Provari, but I can see variable wattage being a benefit, too. As long as I can do the math and compensate for different resistances, VV will do just fine. VW would automatically produce the desired vape.
My Provari can sense the voltage of the battery, the voltage I've set it to vape at, and the resistance of the atomizer coil. A software revision could take those values and produce a variable wattage device. I think they have chosen not to do that at this time, but I see it being possible down the road in a new firmware revision if the market demands it.