Long-term big picture.

When you respond, you make a positive and constructive mental adjustment. When you react, it's purely emotional and rarely does anything to improve the situation; often it makes it worse. That's why they have Emergency Response Teams, not Emergency Reaction Teams.
When you simply react, you go with your gut emotional instinct, with little thought of the long-range consequences.
When you respond, your brain is fully engaged and your self-awareness is high. You have the long-term big picture in mind.