APVs use replaceable cylindrical Li-ion batteries. It is the device that is variable voltage or not, not he battery. For me the biggest advantage of VV is true voltage regulation. I get consistent vapor quality as the battery voltage falls. The second advantage is VV itself and the ability to change vapor qualities without changing resistance of the atomizing device. VW adds another advantage to VV: the ability to change out atomizing devices of different resistances without adjusting output voltage or power.