To me, the HP Professional Satin has the plastic feel Andy describes above. The prints usually emerge from my Z3200 with light surface scuffing as well. So while the HP Pro Satin prints are very nice wrt tones and dynamics, I don't care that much for it.
The PK papers I've liked best are:
Hahnemuhle Fine Art Baryta 325
Hahnemuhle Photo Rag Baryta
Harman FB Gloss Al
The MK papers I've liked best are:
Canson BFK Rives
Hahnemuhle William Turner & German Etching
Crane Museo Max
All these papers have a different look, surface texture, and file rendering.