The advantage with variable voltage (VV) is that you can find the strength (VV) that provides the best taste or vape on the mizer you have decided to use.
There are different types of ecig batteries with variable voltage (VV), some of those can increase the voltage one notch at a time (1 volt) and others have 3 permanent settings. Typically 3.3 V-3.7V and 4.2 V
The regular ecig batteries, when just charged, begin at about 3.7 Volts and declining in strength from the first puff until they are discharged. They offer an experience with less and less "garbage" on the vape.
You will enjoy the experience from beginning to end, as the battery voltage does not decrease when discharged. They continue on the preselected voltage until there is no more current left and you need to recharge the battery.