It seriously depends on how much you're willing to spend. I started with the Lavatube and got 11 friends and family to get them as well since they really work well. The durability is the issue though. Provari V2 is tried and true, time tested and durable as hell with 1 year full warrenty and you can still get them fixed or upgraded anytime after that. My lavatube broke Thanksgiving morning. trigger button failure. granted Volcano was very courteous and helpful, sending me a return shipping label and instructions. The Lavatube 2 is due out any time now, and I've been assured that is much more ruggedly built without the plastic end cap that gave so many people problems and a new trigger button design, much thicker aluminum body etc. That being said Provari is the best if you can afford it. Lavatube 2.0 would be the ONLY other option I would choose if I couldn't afford a Provari.
Furthermore they both have LED displays giving you all the information any normal user could ever need... i.e. battery life remaining, voltage, etc.
Provari even will read the resistance of your atomizer/cartomizer and tell you the rating, ie 3.0 ohms etc. Helpful if you're like me and toss all my cartos in a box till i need one and then forget oh is this one 2.8 or 3.0?