On the arcane guide the priority for any damage spell starts with Arcane Missiles. However, the other guides I’ve seen say not to use Missiles with Radiant Spark up because it eats the spell’s stacks.
Is this just one of those instances where the difference is so low it’s not worth micromanaging?
I can check again, but I found it to be statistically insignificant the first time I tested. Sitting on a clearcasting proc has a cost as well as chewing up the spark charges.