14/8/11 is not possible.
To your question, I'd probably make the 15A 86% one the dragon one. The difference between Dragonite and Rayquaza is small enough that I would want my dragon Rayquaza to have maximum attacking capability. Flying Rayquaza is so far ahead of every other flying type that a small IV difference doesn't really matter, especially since you will only be powering it up to L30 or so. At L30, another ~10K stardust and ~8 candies will give the 13A Rayquaza the same attacking power that a 15A one would have.