I feel that the search volume shown in MOZ is generally low compared to other sources. I feel it is more accurate with search terms that have a lot of volume, but in search terms that are under 1000 searches a month, I start to have a lot of problems with the data. Many times there is no search volume data at all for lower volume keywords which get just a few hundred searches per month or less.
Problems with the volume data effect almost everything else in Moz so I hope MOZ sees this and tries very hard to correct these issues.