Ahri runes

Just want to know which glyph to run on an Ahri rune page. Scaling CDR, scaling AP, or just plain MR.

I feel like the 40% CDR allows more sustained damage making team fights better. Espicially late game. (Been using this since bursting is not the thing anymore) But I find my self dying more without the early MR. As for scaling AP I have not used yet. Don't know if its good.