I'm still testing out the water when it comes to pastels, but I want to share what I've learned about the three types of paper that I have used: Wallis sanded paper, Canson Mi-Teintes, and velour.
Wallis: I took a class on pastels several years ago, before I really got into drawing. The instructor said that a rough surface is best for pastels because the tooth really holds the pigment. Wallis is a great sanded paper, which means it feels like sandpaper. I would go so far to say it eats the pastel. I still had a few sheets left last year when I was deciding whether or not to buy a nice set of pastels, so I did a practice painting. What I discovered was this - the paper really does hold the pastel nicely, but you can't blend it with anything but your fingers (and that hurts after a while) and it's very hard to get a nice, crisp line if you need it.
Canson Mi-Teintes: Since my favorite paper for charcoal is smooth bristol, I wanted to try a paper with relatively little tooth. Mi-Teintes was recommended in several sources, so I got a pack of assorted colors. My first (and so far only) experience with it has been the jaguar painting. Mi-Teintes has a different texture on either side, so I went with the smoother side. Being a pastel paper, the smooth side is still toothy, so when you rub the side of a stick over it you still get patches that don't get filled in. What is really nice about this paper is how you can blend with anything - finger, stump, tissue. I found that laying down a layer of color and blending with a tissue is a great way to get good coverage. And the tooth also lets you put down several layers of pigment before it fills up. My only problem with it is it's sometimes hard to get complete coverage of an area without a lot of blending work.
Velour: I bought a sheet of velour paper on the recommendation of a book I read (and reviewed). My first experience with it was my wolf. At about $6 for a single 19.5" x 27.5" sheet, it's not cheap. It feels like peach fuzz but thicker. It's not very forgiving in that you can't erase. You can't really blend, either, but then you don't need to - the paper does it for you. It's a real joy to work on, and I think the extra cost is worth it.
I know there are more pastel papers out there, but these are the only ones I've tried. If I get around to more, I'll post a review.