With the Sigelei Zmax I can run VV or VW anytime I want. I run it on the power setting (watts or VW) all of the time now. I use both 1.8 and 2.0 ohm cartos. With VV I must adjust the voltage every time I change carto resistance to get the same power (watts). With VW I simply set the desired power I want and the mod will automatically calculate how much voltage it needs to provide to the carto for the power I have chosen.
Also, the Sigelei Zmax won't remember voltage settings (in VV) after a battery is changed. It will default to 3.0V as a safety feature. In power (VW) mode, the Sigelei will remember my power setting after battery changes.
I have always driven manual shift cars. I'd say the difference between VW and VV is more like having power windows as opposed to crank windows. Both will accomplish exactly the same task but one is a lot more convenient. I still need to manually adjust wattage depending on where I want the vapor to go at a particular moment in time, much like shifting gears manually.