RDA comparison.

[tj99959]

I assure you, there are some very different rda's out there, and they are NOT all created equal.
The RM-2 is bottom fed liquid, and the A7 is bottom fed air. Phoenix style rda's are side fed air, and top fed liquid.
The one thing they all have in common is that you can become "self relient", never having to buy replacement heads again. (and that make big tobacco SO MAD)

 

[Thundernoggin]

I just built my first dripper and I'm no expert. But the deck and posts can make a big difference on how easy they are to rebuild. I picked up an Igo-T drilled out to 1/16" from Kidneypuncher for my first attempt and very happy with it.