When paired with a stronger, muscular back, having big pectorals will encourage you to have better posture, as well as making you look taller by adding height to your chest wall. Moreover, having stronger pecs will (obviously) make you more adept at pushing heavy objects, as well as being key muscles used in throwing and swinging exercises. Key bodyweight moves such as press-ups and burpees will become easier, too. Put simply, you will have greater upper-body strength. ~ Berceste