Here is one area where I might say bigger is better, but only to some degree. It still has to fit to your upper body and the length of your arms. Once your mobility is restricted and you can’t make basic movements, or your chest protector rides up your body when you are in a butterfly, It's too big!!! 

 

Your chest protector’s main function is to protect your chest and arms, so when you buy a new chest protector, make sure all areas of your chest and arms are protected (front, back, and sides). Also, make sure the length of the arms and belly pad fit properly,  and that there is padding for your spine on the back that fits correctly.