I now got my Canson sample packs, and printed a test picture on the Canson platine rag, and compared to Hahnemühle Photo Rag Pearl.
I find it quite difficult to separate the two concerning whiteness, depending on viewing light. Also the Photo Rag Baryta is hard to differ. For fun I took spoot readings of the paper whites, and in terms of Delta E the three papers differs less than 0.5, so they're indeed virtually the same. I guess this is as white OBA-free paper gets. The Canson is slightly whiter though.
Concerning gloss and texture the Canson Platine looks very similar to Ilford Galerie Gold Fibre Silk, I like that texture, smoother than Photo Rag Baryta for example. However like Gold Fibre Silk the Platine makes stronger reflections than Photo Rag Pearl, and therefore I prefer the gloss and texture of the latter even more.
I also like the feel of the Hahnemuhle rag better, which is a bit thicker. According to measurements the Photo Rag Pearl has a Dmax of 2.4, the Platine has around 2.2. I couldn't measure my sheet though because the ICC profile from Canson was not so and did not print blacks as black as they can be, a value of 2.2 seems likely.
I would probably choose the Platine over Gold Fibre Silk (as I like the cotton rag, Gold Fibre Silk feels like alpha-cellulose), but when it comes to the Photo Rag Pearl I think it stays as my favorite so far.