As promised, here are my first impressions of the new RR Palo Duo Smooth Rag paper.
I selected on image (a sunset) to print on RR PDSR, RR Aurora Art Natural and Moab Estrada Rag 300. This image was shot on a Nikon Df, processed in LR with final, mostly local adjustments, done in PS. For printing I transferred the TIFF from LR to Epson Print Layout (using an Edit In preset). The settings for all the prints were identical with the exception of the ICC profile where I used the one supplied by the Red River and Moab. For all of the papers I set the Media Type to Hot Press Natural.
Looking at the papers, the base color looks the same. In terms of texture the PDSR is the smoothest, then the AAN, then the Entrada which has a more pronounced texture that the other two papers, but not near as much as RR Palo Duro Etching.
The prints appear to be very similar, but the PDSR and Entrada have a bit more "pop" than the AAN. The PDSR has just a bit more orange bias just as Mark noted in his review of the PDE paper. I think I could be happy with any of these papers for the landscape prints that I make.
This is just my first, unscientific, impression of how PDSR stacks up against these other papers that I have used.