I have the evod, protank2 and the iclear and they're all good. However, if I had to rank, I'd choose iclear, then evod, then protank. Iclear gets the best flavor, airflow and vapor production. It's not exactly pocket-sized though. On the go, and at work, I use the evod. For whatever reason, my protank performs inconsistently and I've read of others having the same experience. I don't think you'll be disappointed going the evod route.
Also, if you're like me, you'll probably just end up buying them all out of curiosity anyways haha.