Madison was telling Cabell to choose? I don't think so.
Madison was using the phrase to describe the difference between the foreign commerce clause and the interstate commerce clause. Madison never said that it was not acceptable for Congress to regulate interstate commerce (he even stated the power could be lodged there), just that he thought it would rarely be used.
It means it is a choice. Just not the acceptable one.
When Madison says "negative and preventive" rather than "positive purposes", does it mean "positive purposes" is also an acceptable choice?