I have both the Buzz Pro and the ProVari; in all honesty, it would be like trying to decide between a BMW M5 and an AMG Mercedes E 550. Do you reall need all the bells and whistles of the ProVari? They do come in handy, but for day to day
vaping, not so much.
There are some out there who swear by the Darwin with its ability to dial in power, but when I plug in a new atty with my Vapemate or a carto with my liquinator, I fiddle with the voltage until I get the vape I want. In the end, I could care less what the voltage is, providing I have the taste I want. In that regard, I give the Buzz a slight edge for convenience with its dial. On the other hand, the button is way too small and sometimes in the dark, it's far too easy to put your thumb on the dial and accidentaly move it. You will not see the light on even a moderately bright day.
LR attys and cartos do not do well on the ProVari, but why would you want that when you have the voltage option? I have not tried any on my Buzz and probably won't since they would most likely blow the atty.
The ProVari, IMHO, may be bulkier, but fits better in the hand.
I know this does not help one bit, but you could not go wrong with either unit.
In any event, tanks and feeders like the Vapemate have made vaping a truly enjoyable experience in conjunction with the VV. If dripping were my only option, I would probably be back to analogs. Drinking and driving are bad; vaping and driving are right behind that, especially with a stick shift.