Actually, I thought it was interesting how different they were, at least in some respects. If you look at the ratio of pre 4.0 versions vs post 4.0 versions, in the Unity stats it's about 27% vs 72%, but on the Android dashboard it's 45% vs 54%.

Perhaps Unity apps aren't as widely used on older devices and thus the stats are skewed in favour of more recent versions of Android.

Then again, the Android dashboard data is collected from the Google Play Store, so it isn't a perfect representation of all Android users either.