I've tried all of them, and I wound up back with poly filled cartos.
The polycarbonate tubing on tanks isn't compatible with my preferred juices - cinnamon flavoring makes it disintegrate. The exposed coil wire baked the juice and made it go bad after a few days of vaping. Replacing the guts is more art than science and they leaked or dry vaped. Scratch tanks.
CE2/CE3 couldn't keep up with my vaping, and I was getting too many dry hits. They weren't convenient to fill and I sweated it out every time I had to travel for work, because the TSA would likely frown on me taking hypodermic & needles through security. I had to snip the top off my juice bottles to end the frustration of watching drips slowly fill the hypodermic every time I filled. That made the cap not seal properly, leaving a sticky mess in my kit. The clear CE2/CE3 also disintegrated with my favorite juices, leaving a sticky mess in my kit. All in all, it was lose/lose. Scratch CEx.
Poly filled cartos are easy to fill. They hold quite a bit, and when they start to run down I just drip a few drops in the top and let it soak in. I get massive vapor and flavor from them. They're cheap, so when they stop working properly I don't feel horrible about throwing them out. For me, they're the best of several imperfect solutions.
I'd love to try an iAtty, but there's no way I'm going to pay USD$250 for a tank mod.