eq does not fight against progesterone sides therefore it would NOT prevent deca dick
most people don't get deca dick and it is usually seen at higher dossages than 300mg a week
diesel,
deca will give you bigger gains if the same amounts are taken, but eq will get you more vascular and can be used for both bulking and cutting
you can also use both if you wish, but eq will not fight against "deca dick"