The reason that the corporate fund (now called Intermediate-Term Investment-Grade) pays a higher yield is that there is some risk.  CD's are insured by the government, and Intermediate-Term Treasury, holding bonds backed by the government, pays about the same.  You can get an extra 2% yield with corporate bonds, but you have to decide whether it is worth taking the risk that some of those bonds will default in an economic downturn.  (You could also split the difference by using Total Bond Market Index, which holds both government and corporate bonds and has a yield in between the two; this is a frequently recommended fund because it gives you maximum diversification.)

What is the rest of your portfolio?  The right bond fund is hard to choose in isolation.