That you have a higher percentage of mothers killing their young than rats.
That mice a far more smelly than rats anyday. They say its the males but I had frozen my male and bought males as needed to service and then he goes too. But I have to say even the 3 females in this one tub with some young are horrible and am going to freeze off the young and the adults as soon as the young start to feed on solid food (1wk or so)....It seems like they defecate more in the corners and let it get a saturated with urine and what not. I have to change them every 2 days to keep the smell down. The .3 mice with babies smell worse than the rubbermaid of 5 rats!
If you can get away with feeding rats I would go for it......If not, then I hear vanilla extract can reduce the smell quite a bit of mice but I can not agree/disagree as I have never tried it.....