Some would say that the Missouri Compromise was a cause of the Civil War, while others argue that it prevented?

The Missouri Compromise was not the sole reason for the civil war. It may have delayed the inevitable. The tensions over slavery were coming to a head.

In the south the slave owners were the ones who were active in government. Large numbers of european settlers immigrated into what was becoming an increasingly urbanized north, while the south remained rural and tied to agriculture. Anti-slavery movements in the north started to influence the political makeup of the country. Thus the Missouri Compromise.

The American political system is based on checks and balances, but it is still subject to favoring areas of high population. Think of New York, Texas, and California as important Electoral Vote states today. The southern slave owners feeling their lively hood slipping away led to the secession of the first Confederate states. Some of the later states such as Virginia joined the Confederacy only because Lincoln violated the US Constitution by calling up the State Militias to stop the legal secession of South Carolina and other states.