There aren't too many differences between newborn Cash and newborn Cooper. I think they'll have very similar personalities but only time will tell. Here are a few of the differences that they do have:
Cooper has more hair and its darker than Cash's was. Although Cash had more hair on his back and shoulders than Cooper does.
Cooper eats well but he doesn't eat all at once like Cash did. Cash would suck down his entire meal in one sitting. Cooper eats in 2 or 3 sessions. He'll eat, back off, burp, squirm and then want to eat again.
Nursing hurts more with Cooper. I never had blisteres or bleeding with Cash. Its probably because Cooper started eating sooner and and more often than Cash did. I didn't have a chance to "ease" into it.
Cooper also had no jaundice whereas Cash did.
Cash was born with very blue eyes - they barely changed color at all. Cooper has very dark grey eyes.