Rats have more body mass and more protein. I believe and prefer our snakes on rats. Even our corn snake. When we first got him he was 6months old and only 15inches long and on 1 pinky mouse a week. We started to feed him 2 pinky mice per week but then tried rats because our friend said that rats seemed to be better for snakes. So we decided "Hey why not, lets give it a try" and we switched to 1 pinky rat a week and (its the same size as two pinky mice) he grew faster and bigger and seemed to be not as skinny as he was when on pinky mice. Now as an adult and almost 6ft he is on a small-medium rat every 9 days.