I'd say the delivery system is going to have more of an influence. If your not already into RBA, I'd suggest looking into it. Can be a decent learning curve, but the results are unbeatable.
The Provari is very consistent, from fresh battery to low. Same vape from beginning to end. This is a big point for some owners.
It can support down to .9Ω coils, which I think is the lowest of the VV PVs.
Those are the only ones I can think of that really pertain to the vapor production end of things. Though, not my entire set of reasoning behind one.
Reliability & construction are what did it for me. After messing up an eGo here and there, I needed something stronger. No more loose buttons, wiggling connectors, fear of it breaking from a mild fall. eGos are tough, and not terribly difficult to fix the minor issues, but it just kept happening. At $20-25 each, already on my 3rd I was already in the price range of a decent mod, but had been eyeing the Vari for awhile. They then started offering the blemished and I went for it.
Affordable future upgrades are another. I think its $20-25 and they'll update your provari (not including the atheistic improvements of v2.5). When they drop the V3, any V1 & V2 owner can have it. They don't have to buy the mod all over again.
1 year warranty, with 2 year available. Some match it, I've only seen one other that beats it (can't remember which mod, lifetime transferable warranty though).