Should we use total return or OAS when comparing different bonds?

When comparing different bonds, for example corporate bonds and Treasuries, should we use total return or Option Adjusted Spread if we want to know one’s return advantage over another?

Some say total return isn’t a good candidate since it reflects yield level change, and corporate bond indices usually have longer duration. OAS or duration-adjusted excess return is therefore a better measure. I don’t quite understand why this makes total return a bad choice.

Can anyone please shed some lights?