Ok I have been mulling over this subject for a while now seeing as it seems to come up here quite a bit , Personally over the years I have seen many more problems with animals fed smaller multiple food items IE intestinal blockage,regurge and so on . I keep seeing the mice better than rats or vise versa comeing up and which is better than which and really I believe as long as you can feed a single food item that has enough mass for good healthy growth there shouldent be an issue .... after all neither rats or mice are on the ball pythons natural menue selection especially the fat and happy spoiled rats and mice found in most pet shops or breeding colonys today. I go on body weight of the snake purely and feed a food item that = 10% of the animals body weight which means as young snakes they get a good mix of rat pups and mice weanlings plenty of calcuim fat and protein ....