Okay the Master Ball has the actual best catch rate, but you only get one of those, which should be saved for a roaming legendary. Arceus doesn't roam.

---

"Things in life aren't always quite what they seem,
There's more than one given angle to any one given scene.
So bear that in mind next time you try to intervene
On any one given angle on any one given scene."
Angles - dan le sac vs. Scroobius Pip