Out of curiosity and with too much time on my hands, I acquired several sheets of Photo Rag Pearl for comparison with Canson Platine. The two papers are very similar, but not identical. Platine is slightly whiter and has tad more stipple to its surface. It may also be a bit glossier, but not enough to be meaningful. Both are cotton rag papers, but PRP seems a bit stiffer. I made several prints using ImageNest on my Epson 3880. Color prints on both papers look quite similar, but Platine shows a bit more fine detail, sharpness and saturation. For this color comparison, I used Hahnemuhle's canned profile and a custom Platine profile, which might have something to do with the color saturation difference, but not with detail and sharpness. I also made some ABW prints, which are again quite similar, but Platine continues to be superior in terms of fine detail and sharpness.
So, my take is that both Platine and Photo Rag Pearl are beautiful papers with many of the same properties, but, at least in my hands and on my printer, Platine is slightly superior. The fact that it is a little less expensive is nice, but it did not influence my verdict.