As for PS-15s, I love them. They feel like all of the other Sanwa buttons.
I used Cherry microswitches on the stick but I need to figure out how to tighten the stick. It feels too Sanwa and I prefer the slightly tighter Seimitsu feel.
Aren't PS-15's Seimitsu? I believe the Sanwa equivalents to the PS lineup are the OBSF-30's (though more like the 14's, and not 15's, in height).
As for the stick tightening, what kind of stick is it, and have you tried replacing the spring? They usually sell stiffer springs separately or you could grab one from another type of stick. I, too, prefer the tighter Seimitsu feel.
Have you ever had any experience with optical sticks? I've been meaning to try one out, but I hear they go kinda wonky after a while.