This assumes you stir the same with the fork and spoon.
You can generally stir more quickly and chaotically with a fork. Stirring with a spoon will require a slower stir to avoid splashing over the cup edge. This ge really means that when you stir with a spoon you create a vortex concentrating the solute in the bottom center of the cup.
There's a reason bakers use whisks and not spoons for mixing - tines create more mixing actions.
You can generally stir more quickly and chaotically with a fork. Stirring with a spoon will require a slower stir to avoid splashing over the cup edge. This ge really means that when you stir with a spoon you create a vortex concentrating the solute in the bottom center of the cup.
There's a reason bakers use whisks and not spoons for mixing - tines create more mixing actions.