In this section, the quality of the implementation will be assessed in terms of the accuracy of the gradients for butadiene. This will be followed by three comparative studies of the different flavors of the CASPT2 and the standard RASPT2 methods. First, an investigation of the smoothness of the PESs at a CI in ethylene and butadiene is presented. Second, the quantitative and qualitative differences in the energetics of benzene are studied. Here the comparison is extended to include the partially contracted NEVPT2 (PC-NEVPT2) and XMCQDPT2 approaches. Third, the effect of the state averaging in ethylene is put forward.