One of the reasons for the efficiency of automated theorem systems is the usage of good heuristics. There are different semantic heuristics such as set of support which make use of additional knowledge about the problem at hand. Other widely employed heuristics work well without making any additional assumptions. A heuristic which seems to be generally useful is to "keep things simple" such as prefer small clause sets over big ones. For the simple case of propositional logic with three variables, we will look at this heuristic and compare it to a heuristic which takes the structure of the clause set into consideration. In the study we will take into account the class of all possible problems.