The advantage of a vv battery is that if you have different resistance *omizers you can use Em. I my nova came with 3 heads, and I can use all,3 because I can adjust the voltage. I I also have some lr cartos in my rotation so I can switch it up from lr to Sr, to my clesro and I'm all set. The also as mentioned some juice tastes good at 3.2v others at 3.8 so you get some ability to test. I with s fixed voltage batter none of the above is possible