That's a good question. Here in South Florida I don't have to worry about keeping chickens warm, so I just give them cracked corn for an occasional treat. The cracked corn is cheaper than the mixed scratch, which has corn & other grains & seeds mixed together. I use it for training purposes, to reward them for coming when I shake some scratch in a can.
With chicks I would give them just a little, for training or for a treat, I think they should eat mostly their chick starter to help them grow.
Be careful about givng scratch or cracked corn to the little ones. We lost two polish chicks from giving them one brand of scratch.I now use Nutrena it is called scratch grains. it is much finer and easier to digest. Mine are spoiled I give it to them in the evening while I am collecting eggs. I limit giving it to the younger ones though. How old are yours.