The Kayfun Mini and Dripper Spiral/Pro are my two favorite RBAs. The Kayfun Mini set up for drip mode (including a drip tip) is only longer than the Dripper Spiral if you don't use a drip tip on top of the Spiral, which I do.
As much as I like my Drippers, they're my second favorite RBA. The Mini's advantages, as I see them:
- center post - Kayfun Mini is adjustable, Dripper isn't and all 4 of mine are long
- airflow - Kayfun Mini adjusts like the 3.1, Dripper doesn't at all
- setup - on the Kayfun Mini your only limiting factor is really the space of your work deck, your options on how to build the Drippers are limited
- configurations - want a tank? screw another piece or two on your Kayfun Mini, or look for another RBA to swap your Dripper for
- build difficulty - no need to join R/NR wire on the Kayfun Mini
The places the Drippers win over the Kayfun mini (for me) are price, availability, and looks. I like both a whole lot, but if I had to choose only one? Kayfun Mini all day e'ry day!