>>333204813 year SQ-A owner here.
S vs PS doesn't really matter. Don't pay a premium for PS lenses. The 80mm is a perfect standard lens for the camera. If you prefer the 35mm focal length, try to find yourself a 65mm.
Aside from the 40mm and 35mm, all S lenses are 67mm filter size. Going to PS changes a few.
Fwiw I have a 50mm S, 80mm S, and 150mm PS.
Pic unrelated