Male mousies are more fun; almost all my faves over the years have been boys. They like to play and are eager to come out and climb all over me. I have a couple of lines in which the boys live peaceably with their fathers, even when one of them is taken out to stud and put back after a couple of weeks. I've only had a handful of does who were really ready to play and actively sought out The Hand. As I don't routinely cull unneeded bucks I have a lot of them, and there's a limit to how much space they can be allowed to occupy. I try to house them in close quarters until they are past 6 mo. of age and gotten past the testosterone surges that come at 10 to 15 weeks. Once they are over adolescence and remain nonviolent, then I consider putting them in a bigger tank. There are occasional scrapping over tasty bits of food, and I keep a close eye on my boys (all my meeces, actually. I love to watch my mousies interact) and the ones I don't want to breed may be culled if they start acting up. The ones who do fight are very likely to be held back from breeding unless I really, really need their contribution in a project.
BTW, laoshu: WOWSERS! Boing boing boing! wanna get one or two or three...