In this paper, two classes of approaches to include PMU measurements in the power system state estimation are analyzed and compared in terms of accuracy and adaptability. These state estimators (SEs) are evaluated by considering measurement containing Gaussian errors and the three main methods presented in the literature for measurement standard deviations definition. The main found is that the standard deviation calculation approach needs to be carefully specified in order that the SE performances are evaluated in a fair way. Besides, the One Phase SEs show to be more accurate and the Two Phase SEs are easy to implement. Test results on the IEEE14-bus system are presented.