PSS/Transient Spectre/APS discrepancies

I'm running a simple circuit with PSS. I decided to compare the results to Transient, and found that they differ by a significant amount. My output amplitude is 783mV with PSS(spectre), 772mV with Transient, and 754mV with PSS(APS). I ran the transient out for a long time to make sure a steady state was reached. How do I know which is these 3 is the correct answer?

Thanks,

Steve