Hi, welcome to the board and great name!
The way Wrathful Strike works is that you commit 2 dice to the attack, but only one counts for the attacking part. The other ensures an extra die of damage if you hit.
So the difference is, if you are making two strikes you’d be making two separate attempts to hit, each of which will cause damage if you hit the target. With the Wrathful Strike, one die is the attack, the other just represents the expenditure of one more MP for extra damage. If you got the first hit, the extra damage is automatic.