I have the Extreme Vape as well. I like it better than the Volcano. It's easier to fill and empty, it's half the price but better craftsmanship, you can vape or use whip. A year ago I accidently short circuited my power adapter by plugging it into a wall with bad wiring. I e-mailed Arizer (bought the unit off Amazon) and they sent me a new one, along with a few extra screens. Good support. Good warranty. I'm a total fan of the Extreme Vapes.
The only edge the Volcano has is the stock bags are bigger. Funny thing is, the Extreme and Vaporizer bags are really just turkey oven bags. I bought some extra large bags and I've been using those ever since. $3 for a pack of 10 bags! The Extreme Vape just has a glass tube with a strong rubber band holding the bag in place (which as weird as it sounds, its strong enough because I've completely forgotten about them before and the bags don't pop)
With the Volcano I believe you have to use their bags because of the special attachment. If you want larger bags you I heard you have to buy expensive aftermarket ones that come with remanufactured tips. So i dunnoo... $600 for a Volcano or $300 for an Extreme Vape??? Buy what you like, but if mine ever breaks I know what I'm buying again.