Well, for build quality, I can attest to the Vamo being at least sufficient. I have dropped my Vamo V3 several times on to concrete and it survives (albeit a bit dinged). only concern was the tube is not glued on, but just pressed on. I... <gasp> took a mallet with a wooden block and hammered the sucker straight again, and it is just as good. (had to get a new glass tube for the AGA though).
Brass threading on the Vamo's 510 might be a concern, but I am overly cautious with anything screwed in anyways (cross threading is one of my pet peeves). I cannot attest to the QC of the Vamo, since both of mine have been good straight out of the box with minimal complaints (the V3 stainless had a shaving on the battery cap connector).
Price is a concern. from FT, I get the Vamos super cheap (albeit one month later). Time is not an issue, but price sure is. Just going by price alone, I'd have to warrant the extra $150 for the provari. Even if it is a better device and better build, a %600 higher price is a tough hurtle to leap over. I could almost have a different Vamo per day, or use one Provari throughout the week.
As far as the voltage regulation, I can't attest to a better vape quality since I haven't tried. I've rarely heard "the rattlesnake" sound. I think it only comes when the battery is low. the better vaping at lower battery power is both a good thing and a bad thing. I do notice when the battery gets to 3.5v, the vapor production is quite a bit less, but to me, that's an indication that my battery is getting low. I would imagine that is what people who use mech mods base their battery level on.
thickness of metal, again, a plus and a minus. thicker metal makes the mod heavier. If the vamo had thick metal, it'd be a beast to hold. The Provari, I would imagine, would be a similar weight, since it's a shorter mod, but with thicker metal.
The fact that it's made in the USA is definitely a plus when it comes to the Provari. Although I'd like to buy from the US when possible, in most cases, price point usually directs my purchasing decision. To me, that's a problem with our US mentality that's a more philosophical debate not really suitable for this forum. China can produce something much cheaper because of labor costs.. It's really surprised me that they haven't made a Provari clone with comparable electronics.
I guess in the long run, if you take the price out of the equation, the provari is a better device. But if you take "bang for your buck" into consideration, then the Vamo wins. Both have their shortcomings.
