Is there a functional difference between "all" and "each"?
There is no functional difference between "each creature" and "all creatures" in MtG rules.

The difference here is grammatical :
 - "All" considers creatures as an ensemble
 - "Each" considers all creatures in a group individually

So an effect that is usually considered "global" will use "all" :
 - Destroying a bunch of things -> Wrath of God
 - Giving a group of creatures -X/-X -> Engineered Plague

While effects that are relative to each permanent will use "each" :
 - Dealing damage -> Deafening Clarion
 - Giving some creatures +1/+1 or -1/-1 counters -> Song of Freyalise or Harbinger of Night