contrast:the opposition or dissimilarity of things that are compared
balance:harmonious arrangement or relation of parts or elements within a whole
constrast meams you would compare all the alternatives and figure out the advatages and disadvantages for each one.And finally u may only choose/emphasis on one only,and the other may just serve as the supporting role.
balance means you put all alternatives together in a harmonious way.U choose all of them.They are equal to each other and support each other.
An example in cooking food:
【A good recipe needs both contrast and balance】.
Contrast in texture,as in a soft rice pilaf with the crunch of toasted nuts; contrast in flavor,as in a sweet mild cheesecake topped with acidic strawberries; and contrast in temperature,as in a smoky grilled steak served with cold salsa.Yet these recipes also need balance:sweet balanced with salty,sour balanced with earthy,acidic balanced with more sweet.When a recipe has contrast and balance,it's a pleasure to look at and eat.