Pro Staff's were lighter, headlighter, much less durable in the whole racket from head to throat, and better for weaker players to compensate for the extreme weight and stiffness of the K's and SSmiths.
I used PS's for a couple of years, at 5'11" and maybe 130lbs., and they were great for 3 string jobs max. After that, they'd get soft or often crack mostly at the joint between head and throat.
But that was fine, as they were light and manueverable, quick and solid for it's lifespan.
My dad used to play w/the JK Autos and I tried them a
few years ago. Then I founda JK PS and played with that.
JK PS: came in various weights. ranging from 12.0 oz
to 13+. Much stiffer throat b/c it has an addition piece
of wood on top of the throat area above the grip.
To me it was much more stable and had better feel.
JK Auto: also came in various weights. less stiff and felt
like a wet noodle compared to the JK PS. It also came
in a "midsize" version that had a larger head than the
std wood racquet size. The midsize appeared to be
close to the PS85's headsize but was more round in
shape.
I think Johnny Mac used to play w/a JK PS at some point.
I played a wood racquet tournament for fun a few years
ago. I used a JK PS. By the end of the tournament the
strings had ripped through the wood almost all the way
through at several places. After having so much fun w/the
wood racquet in the tournament I started collecting a
bunch of them. I'm going to try and get into the wood
racquet tournament in palm desert they have every year.
I'm thinking of organizing
one in LA w/the proceeds going to a charity. Maybe
something like Habitat for Humanity since I've always
wanted to volunteer for them.