Previous work to use the SMx universal solvent models to predict limiting activity coefficients is limited. Recently, Lisboa and Pliego used SMD to compute 46 limiting activity coefficients. In the present study, we compute over 3000 limiting activity coefficients with comparison to reference data, for each SM12, SM8 and SMD. In addition, we compare two methods of calculating the limiting activity coefficient: 1) The solvation free energy and self-solvation free energy were both predicted and 2) the self-solvation free energy was computed using readily available vapor pressure data. To better understand the two methods, we compare the individual contributions of the solvation and self-solvation free energy to available reference data. In general, there is not a significant difference between the limiting activity coefficients computed using the two methods. However, for the cases in which water is a solute, the results are significantly better when both the solvation and self-solvation free energy are predicted using SMx. This results from a cancellation of errors in the two terms. We therefore recommend that in general SMx be used to predict both the solvation and self-solvation free energy when computing limiting activity coefficients. Comparison is additionally made to predictions using UNIFAC and MOSCED. SM12 and UNIFAC are found to exhibit comparable performance, motivating future exploration and research into the viability of using the SMx models for phase equilibrium calculations.