A plasma simulator which employs efficient numerical methods is used to do parametric studies on an electropositive (Ar), and an electronegative (SF6) discharge. The effects of pressure and current amplitude variation are studied; the phenomena associated with the transition of the discharge into different operating regimes at low currents, and at high currents, are demonstrated and discussed. Comparison of the model results with experimental data is good. The effect of ion mobility variation with electric field is also studied, and is shown to be important in improving the comparison with experimental data. Finally, a sensitivity analysis on the values of the transport and kinetic parameters is done. The sensitivity analysis and the agreement with experimental data demonstrate the validity of the continuum modeling approach, as long as reasonably accurate experimental data for the model parameters are available.