MCN's are Modern Cloth Nappies ie. the fitted styles, All in Ones (AIO's) or pocket style.

This is a quote from Indira Naidoo - journalist
"Traditional nappies can take up to 400 years to break down," explains Naidoo. "About 95 percent of Australian parents use disposable nappies, which make up about one percent of the 22 million tonnes of landfill waste each year."
So yes 1% doesn't sound like much but it is still 22,000 tonnes of landfill each year. And depending on the type of nappy they can take up to 400 years to break down.

Most of the research satying there is little difference environmentally assumes the old style flat nappies that require soaking, bleaching, hot washing and drying in a clothes dryer. However if you use the MCN's that only require dry bucketing, no bleaching, cold wash and line dry then most of that imact is cancelled out.