It depend on what technology you plan to use for your design. If 0.18u, 0.25u is your target process, the MOS model may be a problem due to lack of MOS model support in PSpice. If 0.5u, 0.8u or 1um technology is your target prcoess, it should be OK. I knew that some power-management fabless design house used PSpice to do their design here.
Should be the same, it the model that will determine the accuracy. I had tried simulating my circuit in Spice and Pspice before, there is not much different in the result.