Well, quite simply, the difference is everything.
If you envision a body of water, and it’s deep enough, then a reaction would be akin to the surface of the water. It’s constantly rippling, moving, and changing — it’s rather chaotic.
Whereas the depths, the water down below, is calm, stable, and quiet. This would analogous to a response.
When you think about where each comes from, there’s another facet of this analogy. A response requires depth, patience, and diving down into the calmness of being. A reaction is quick, unpredictable, and uneven.
It is always better to respond when you find yourself in situations where a quick reaction is the easiest. Sometimes a reaction is required — but overall, the goal should be to get to a place where a moment of calm… then a response, is your automatic go-to.