Because of the generally high credit quality of money market debt and its short term, this is among the least risky of fixed-income investments. The interest on Treasuries is exempt from state and local tax. Since the federal government issues them, Treasuries have very low risk. Unlike Treasuries, they are not government-guaranteed. Municipal bonds are issued by state and local governments.
Most municipal bonds are exempt from federal tax and many are also free of state and local tax.
Corporate bonds are issued by corporations. Your rate of return will depend on the creditworthiness of the issuing corporation. They are fully taxable. It's easier to select individual stocks than bonds. Second, while much information is publicly available on stocks, it is not so easily obtainable on many fixed-income investments.