Within the framework of a simple molecular thermodynamic model, the problems of comparing equations of state (EOS) and the choice of analogs in three sets are analyzed: equations based on the model of interacting point centers, van der Waals type equations, and Martin equations derived from volume translation. A method for the selection of EOS was proposed and approved by calculating the critical isotherms Ar and C4F8. According to the results of the PV calculations, the selected EOSs turned out to be better than known those of Peng-Robinson, Martin, Redlich-Kwong. On the basis of a new characteristic of the equation, a parameter comparing the configuration contributions, a method has been proposed for choosing EOS-analogs in different families. An explanation is given for the impossibility of describing equally well with one equation two states with a reduced density of 2 and 3/2. The results obtained for the EOS of the new model confirm its adequacy in full accordance with the method of abduction.