Fixatives: Powdered or Cut?

Could you tell me if orris root powder is superior to cut orris root in conveying and retaining scent in potpourri? I just read that it is. Am hoping what I read is wrong. I find that the powder coats the materials to a degree and therefore doesn't look as attractive. I am trying cut orris for the first time. Perhaps more of the cut root is needed to achieve the same effect in scent?

Powdered material has more surface area per unit weight than the cut form. Because the retention of scent is a process involving the diffusion of volatile oils in and out of the fixative material, the more surface area is exposed to the volatile oils the better. It makes sense then that the powdered form would be a better store of scent-producing molecules than the cut form.

Also do you know if orris root is superior to calamus root as a fixative in potpourri?

I don't know that one is better than the other. Joanna Sheen, in her book "Potpourri" (Cassell, 1994) says that orris root and calamus are equally good, in both their powdered and cut forms. Barbara Milo Ohrbach, in her book "The Scented Room" (Clarkson Potter, 1986) says this of orris root: "There is one drawback, however: in its powdered form, orrisroot can make your potpourri look dusty if you use too much."
Other options for fixatives are benzoin, vetiver, oakmoss, and storax. Sheen suggests trying other roots such as rhubarb root, sarsaparilla root, wild yam root, angelica root. She also recommends a cellulose product made from corn cobs.