Cacao is uncooked. Cocoa is the cooked/roasted product. Cooking/heating anything changes it, often completely. That's the difference you are tasting. But a better comparison would be between adding cacao powder and cocoa powder (not the Dutch variety) to your quinoa.
Cocoa powder (regular) comes from beans that are fermented, dried, roasted and cracked into nibs.
Cocoa powder (Dutch) starts with cocoa beans that have been washed in alkaline solution of potassium carbonate. This wash neutralizes their acidity. They are then processed as above.
Cacao powder comes from the unroasted beans, that are still fermented...