The Lavatube. It's been particularly refreshing from a switchover from the eGo batteries. The VV is easy to use and get's (from 0.1, adding and decreasing.) that perfect strength right off for the atty I use. The biggest thing I'm happy with, however, is the fact that it's easier to charge, in my opinion.
The chargers for the Ego batteries are.. flimsy.., Not so with the Lavatube, it.. Well, it charges like you charge a AA or AAA Battery. You don't have to worry about screwing it in too tight by accident, or breaking the plastic, or for your Battery's plate corroding or burning. That's legitimately my favorite part. (Even if it does take a bit more work to charge the dang thing, it's still better than screwing the battery in to the charger)
I also had an Ego-T, when I first started vaping that just plain fried randomly, and, after talking to some people, the cause is still unknown. It was quite a let down, the case of it got hot and just.. Eughk.. I haven't had that issue with the Lavatube, though. It's built sturdy, I think. It's built well, inside, and out. I was.. ehn.. when I was reading the reviews.. Full of crap.., But, having actually bought it, and had my own few accidents? Yeah, I love this thing. I'd recommend it to anyone.