Ok I can see the material making a difference since the case is actually the negative side of the battery and thus adds resistance. The series/parallel part I said assuming the same battery, meaning comparing single to single mods, series to series, and parallel to parallel using the same batteries. Of course a 2 battery mod would be different from a single, etc.
Compare the noisy cricket to the VCP. You'll know a difference, especially because one of them is a handgrenade