I think there are *different* pin codes floating around with varying %s.. So I think the answer is, it depends which pin code a person has, whether it was better or worse than the GP code.
For me, I booked on a pin about a week ago for 2 nights at CBR. I am paying roughly 130 a night. The GP code quote I got yesterday came out to be about 110 a night (incl. tax)... so the GP code, in this case, worked out to be a better nightly rate than the pin code I got in the mail.
However, I couldn't use the GP code because it has a 3 night minimum on it, or so I was told... so I stuck with my pin.
Hope this helps.