Note: I live in a state that doesn't have a state income tax, so there is no advantage to holding US Treasuries vs. CDs. In states where there is an income tax, interest on US Treasury securities is usually exempt from the state income tax. You need to factor that into your calculation.
I don't hold corporate or municipal bonds because of the default risk, however small. Since I view my bond portfolio as a haven if we have a repeat of "the Crash of 1929", the small additional yield isn't that attractive to me. My preference for US Treasuries and FDIC insured CDs is meant to protect the absolute downside.