Final answer:
The Missouri Compromise balanced the interests of the North and the South in Congress.
Step-by-step explanation:
The pro (benefit) of the Missouri Compromise was that it balanced the interests of the North and the South in Congress. By admitting Missouri as a slave state and Maine as a free state, the compromise ensured that the Senate would maintain a balance between free and slave states. This helped to prevent one side from having a significant advantage over the other.