rats have a higher fat content than mice and you will see a noticeable growth rate between rats and mice, and as everyone has already stated its nice to only need to feed one prey item vs. 2+, i breed and feed asf's for my collection and i find a higher growth rate with them than norway rats as well, that and i have no picky feeder issues, and the snakes put more of the rat to use (they poop less) and an adult asf is a perfect meal for an adult ball, aslo mine will produce up to (on average) 20 babies every 21 days.