I used the eGo T and then the VTR with Protanks. The VTR has been disappointing to me. That swiveling wheel where the tanks connect is a constant source of issues. Resistance jumps all over the place. Smooth good vape one minute, burnt, nasty crap the next, all without doing a thing.
I've now switched to two PV's, both using mech batteries. The first, is an RDA (Rebuildable Drip Atomizer): The IGO-T. This style is the one people use for making big clouds. You can get big flavor also. Very satisfying. Being that you just drip the juice in when you want to vape it, there's no tanks to clog or clean. It can get a bit fumbly and messy, and you get just a few hits off of it before you have to open up and re-drip, so not the greatest for on the go.
My other is also a rebuildable, but is enclosed with a tank: Kayfun Lite Plus. This is great, and pretty much perfect for on the go vaping. Tons of flavor, great clouds, and holds 4.5 ml of fluid (enough to last a long time).