Whenever you hear talk of fine paper, Clairefontaine and Rhodia will always come up. What's confusing though is that some people know the difference between the two, and others don't, so rumors spread. Well I'm here to clear up some of the confusion between the two brands.
Clairefontaine has been making paper in France since 1858, and Rhodia has been making paper (also in France) since 1932. In 1997, Clairefontaine bought Rhodia. Their products have been long established so the brands are separate, but Clairefontaine is the parent company. The paper in the Clairefontaine notebooks and Rhodia pads is all made by Clairefontaine, but it's not the same paper.
The Clairefontaine staplebounds are smooth, 90g paper, ideal for fountain pen use. The paper in the Rhodia pads is 80g, and slightly less smooth, ideal for fountain pens or pencils. That's the big secret! There's really not much more to it than that. If you see a 90g offering within Rhodia, that's Clairefontaine making the paper.
There are a whole variety of different products under both brands, which might meet your needs based on your individual preferences. Check them all out for yourself and see what you might like now that you know what's up with both brands!