Meh, preference of one over the other is just that....personal preference. I prefer VV.
With variable voltage you need to know the ohm resistance of the coil you are using. Pressing both the + and - button simultaneously will give you the puff counter, and then the atomizer reading in ohms. Then you need to do some first grade math.
Ohm plus the number "2" will be the voltage to use. (2 ohm + 2 = 4 volts). Or, you can just start low in voltage and work your way up until you find your sweet spot.
With variable wattage, you'll need to know what your sweet spot in wattage is already. Say you like 7 watts. Set it and forget it. Even if you switch tanks with a different ohm rating, the circuit board recognizes this, does the math and resets the output so that you are still
vaping at 7 watts.
You will always be in either variable voltage mode or variable wattage mode. Not both. The last setting you make, you'll remain in that mode until you make further changes.