Always have been more comfortable with VV. I started with ego twists, bought a Provari, got real comfortable with VV, then bought an MVP2, and always switched to VV because that's what I know. I understand the merits of VW, but I pretty much have a mental picture of what volts I need to go with for what ohms my different devices run. Never bothered with the charts, just learned and now, the proper adjustment of my volts is just second nature.
Nothing against Variable Wattage though. As I said before, I'm just more comfortable with the tuning process of voltage. I know that if I run a protank II with a 1.8 ohm coil at 5.7 volts, you will see me in the hospital tomorrow haha.
Do what works best for you. As other people said, it's essentially different methods of accomplishing the same thing. And it was also stated that no 2 devices are different.
I run my 2.5 ohm RSST coil at 6 volts. Try that with a Protank II 2.4 ohm coil. I run my 2.0 ohm Kayfun coil at 4.2 volts. I just adjust to my needs. Works for me