Well, it certainly *seems* like the PaloDuro is the same as Epson Platine (more so than Canson Platine) for a whole lot less $$$ (13x19: $78 vs. $130)
Great sleuthing Ernst!
Yes, the RedRiver looks like another Schoeller Platine-clone, and good to see that.
It isn't an especially great deal when you compare it to the price after the current Epson 3 for 2 rebates. Yes, rebates end, but discounts from competing suppliers do not, and afaik, RedRiver papers are just from the one source with its fixed prices. I use a lot of 44" and the math is clearly with Epson Legacy Platine at moment.
Don't dismiss Canson Platine white point - it has improved a lot as Schoeller is getting better at grading its cotton and base coatings. The Platine white point has got notably higher (bluer) since its introduction, when it was a unique paper on the market. It's an ever improving Platine paper base that is available to all, clearly.