As of I know, there are no differece between them except the size and shape. I think that usually english mice are what are usually called "fancy mice" at pet stores. And american type of mice are sold as "feeders". Here, they have them all mixed up so when I bought my mice, they all cam from the "feeder" bin, where there were lots of different colors. I got Cheddar as an adult, and since she had never been held before, she's not tame and doesn't let me handle her, now my other 3 mice; Brie, Ricotta and Muenster, came as babies and I've handled them every day since I got them and they let me handle them, but they are not tame as to say that they jump on my hand to greet me (working on that, though). Mice are the shortest lived of the rodents, but can live 2-3 years if cared for properly (average is 1-2 years).