The Infinity Pro is the latest generation of the Buzz Pro. Same electronics, 3 Amp limit vs. the Provaris 2.5 amp. And the Buzz/Infinity use a Buck Regulator which is more efficient than the Provari's Boost Regulator. Less wasted heat and longer battery life.
And the Buzz/IP use a simple thumb wheel to adjust voltage. Faster and more intuitive for many than the Provari's buttons. The provari does have a digital display for voltage and resistance which the Buzz/IP doesn't (need : ).
I chose the IP over the Buzz for form factor, very cool looking to me in chrome with chrome caps. And over the Provari for efficiency, maximum power, and ergonomics.
There's a lot of choices out there.