Your battery IS YOUR PV... The rest is all about getting the current from your battery to the heater coil. Every PV on the market does this reasonably well. Some are better than others, but all do it acceptably well.
Everything else is window dressing... all of it.
If you go to the mad vapes site, and buy a Bolt PV for 40 bucks, and stick an AW 18500 battery in there it's going to vape EXTREMELY well... if you stuff a cheapie battery in there it will become lackluster in performance and safety is out the window.
Changing ONLY the battery makes the difference between a super safe and well performing device and a dangerous pipe bomb that doesn't vape all that well.
I agree. I have a couple of Maxi RoughStack V2's that are home-only pv's. I run 1600mah AW IMR 18650's in them both and they work very, very well. I've run them with Ultrafires, generics, and 4.8 NI-MH's with spacers as well with results ranging from acceptable to poor. I find that the AW's give me the consistent vape and seem to perform best in terms of steady discharge rate and battery life.

- Tim