What is the strongest brand of e-cigarettes?

I have bought the Daje e-cig kit. So Far I really like it and have been using it for two weeks. I charge it at night and use it during the day. the cartridge thing that you screw on is like the filter and it has a soft shell so it feels kinda like a regular cigarette. my brother has the kit from blu and that one is a hard plastic kind. i didnt like that one so much.