Well I'm not Hirsch, but this is how I compare them: 
 
PS-1 > RS-1: 
 
PS-1 is better at resolving subtle details, has a smoother frequency response, has less of a bass hump, sound stage is a more laid back and 3-d, highs are more accurate and under control, no sibilance problems, bass is more detailed and goes lower 
 
RS-1 > PS-1: 
 
RS-1 tone for wood and stringed instruments sounds more true to life, quantity of bass is more accurate 
 
And I still listen to them both.  
 
Biggie.