I have lived in both Champaign and Urbana, and I prefer Urbana's schools. Champaign didn't take much time to help when my son encountered some problems, but Urbana was much better in that regard. However, I have to agree with the other comments: Mahomet, St. Jo, Monticello, are all probably better options for schools.
Crime rates b't Champaign and Urbana are probably really similar - the towns are so intertwined.
There are no city taxes here - only county taxes.