Matt,
The benefit depends on where the cities are located and what type of terrain they are on.
In general, you should look at concentric rings of cities around you Capital or City with the FP. These two cities define points of very low or almost zero corruption and waste.
If you move out in a radius of 5 tiles, this is a primary core that may not need the courthouse and police station to be productive. The benefit gained from these two improvements may not be enough to offset the maintenance costs and the production/sheild investment.
Out between 10 and 15 tiles the benefit of the courthouse and police station is usually measurable. At distances beyond 15 tiles you will need to think about the purpose of the city because these frontier cities can rarely produce improvements in a timely manner. If it takes 120 turns to build the courthouse in the first place, there may be too few turns left after that point in time to ever recoup your investment.
If you are in democracy, the propoganda suppression benefits of the courthouse are never needed.
In the past, the main reason to research communism was so you could GIVE it to your enemies, because they would switch to it during wartime and commit suicide in everyone of their cities by destroying their own people to build units.