over all i think rats are healthier, being that they have plenty more protein and less fat. I mean, dogs,cats and humans can even live on an all rat diet and live. Rats exercise more (when not in a small space) then mice do. More protein means more muscle mass for our snakes. like us, when we are more muscle (not body builder muscle) human tend to be more fertile then those woman on a bigger side. though when it comes to breeding its easier to breed mice and asf ahaha they tend not to bite the bejeebus out of everything.