Every time when I offered my ball python a small adult mouse he would just take it, but when I sometimes offered a weaned rat he would look at it acted like he's interested but he would never strike at it.
I'm sure my ball python eat both rat and mice because when I first bought him I went to pet smart and got him like two small rat and he ate it.
Side note: I got my small adult mice and weaned rat from online from bigchessefactory and they all white in fur. The small rat I got from pet smart had different color in term of fur.