Existing DSMC phenomenological models for vibrational relaxation and dissociation reactions are implemented in a three dimensional direct simulation Monte Carlo code. A modification to an existing inelastic collision selection procedure is proposed. The proposed selection procedure simplifies the calculation of the collision probability. The selection procedure no longer depends on the relative order of rotational and vibrational relaxation and no longer requires the solution of a quadratic equation for every collision to determine the inelastic collision probability. The proposed selection technique is validated to accurately simulate rotational and vibrational processes for gas mixtures through isothermal relaxation simulations compared with analytical solutions. Using the proposed selection procedure as a consistent framework, four existing DSMC models for vibrational relaxation are compared using both isothermal and adiabatic relaxation calculations as well as 1D stagnation line simulations for hypersonic flow. Furthermore, using a consistent vibrational relaxation model, the Quantum-Kinetic, Total Collision Energy, and Vibrationally Favored dissociation models are compared for 1D stagnation line hypersonic flow.