Cosmo (Fairly OddParents) vs Bill Cipher (Gravity Falls) — who wins?

Let’s say it’s a full-on magical showdown: Cosmo from The Fairly OddParents vs Bill Cipher from Gravity Falls. Both are in-character but with access to their usual powers — Cosmo has fairy magic (wish granting, reality manipulation, etc.), while Bill has his insane dream demon abilities.

Who actually wins here? Does Cosmo’s rule-based fairy magic stand a chance against Bill’s chaos-based reality warping, or does Bill just erase him from existence?

Would the Fairy Rules or Da Rules book limit Cosmo too much, or could he technically wish something that stops Bill?