I have the Darwin as well as a VAMO and have vaped on a Provari. Both the Provari and Darwin are top of the line in build quality. But personally, I would take VW over VV if the price difference was small for the advantages of variable wattage over variable volts. But you can't go wrong with a Provari.
On the price difference, to make a fair comparison, when you add in the cost of the batteries and charger and extra cost for the 2nd year of warranty for the Provari that is standard with the Darwin (2 year warranty standard), there really isn't that much of a price difference.
Along with the variable watts feature with the Darwin, I like the USB charging capablity, being able to charge and vape and never having to carry extra batteries. Although I get 18-24 hours on a charge so it's only a small advantage unless I forget to charge it one night. I also have found it to be pocket friendly due to the flat shape. But as mentioned above, you can't close the arm if using a tank, which I do at times. But that makes it the same approximate length of the full provari with a tank in your pocket so I see that as a wash. I really do like how it lays flat on a table, etc. I don't know how many times I've gone chasing my tube mods as they rolled away from me which is never a problem with the Darwin, lol. Also, the Darwin battery comes with a one year warranty. I've been using mine for two years of heavy vaping and it's still going strong with only a slight drop in length of charge held.
Both are excellent PV's with pros and cons for both. I do think you are going to be seeing more VW model PV's and less VV ones as time goes on.