Provari just overall makes you happy.
I have both the Buzz & Provari and both are quality PV's and both pretty much vape the same in my opinion. The Provari has a couple of features more then the Buzz with its LED screen, if it's important for you to have this feature then I would say buy the Provari and pay a bit more, however you can also spend a bit less with the Buzz and get the same vape and check all the same features as the Provari lets you do by using a meter. I'm using both on a daily basis and like I stated there both quality PV's that give a great vape especially when you ad a VapeMate to the top of either unit.
The single battery design on the provari is enough of a bonus to get the provari alone. I don't have a buzz but I have a jokerav. I believe they are very similar in construction. The battery options are limited to 800mah or so on my joker. The regulator steps voltage down from 6v to whatever you have it set. This works well but there is a drop off once the combined voltage drops below your set voltage. The provari steps voltage up with no drop off and shuts off once min safe voltage is reached. Also allows for higher mah ratings. Money is the only issue. I think as a device provari wins every time. All of the other features are just icing.