The differences wasn't huge, but the depth was still deeper on the HP1000s to my ears.
The top one is the HP1000 and the bottom one is the GS1000 (measure very similarly as the PS1000s).
The very natural treble of the HP1000s was also quite good. Joe Grado really had an ear.
FWIW, GS1000 vs. PS1000:
Very close measuring and sounding, but I do slightly prefer the PS1000s, but the GS1000s are sure light and easy on the head WRT comfort.
Not trying to be a smart *****, but i don't care too much for graphs, i believe that it's the sum of the whole system that counts, if you have a brighter sounding source, a neutral amp and headphones with a rolled off treble, the en result might sound very good, even tough two of it's components don't have the flattest frequency responce. And even if the whole system ends up being far from flat, it's still might sound good to some people. Also if they told the whole story, most Grado headphones would be unlistenable, but i admit that i'm surprised that, on paper at least, the HP1000 do seem to have more bass than either the GS and PS1000.
It's not hard for me to understand that you, and many others i'm sure, prefer the sound of the HP1000 over that of the PS1000, the HP1000 are wonderful sounding headphones. And like i said, it's not a night and day difference, and to tell you the truth, i consider myself very lucky to have the liberty to chose between these fine sounding headphones for my listening sessions, it's a nice ''problem'' to have. Even my SR80i bring a smile to my face everytime i put them on, my GS1000 are the ones that get the less headtime.
There's nothing i like more than to reading positive comments where people have found the ''perfect'' headphones for them, i have, and mine are the PS1000, by a hair