I've never paid attention to any distinction of luxury vs. stiff that is indicated on the Darice web site. Though the cards have changed through the years, I continue to look directly at the fibers just as AtticaFish does.
Sometimes, there is variation in color or stiffness between lots of furs depending on your supplier(s). I have several patches of brown that I consider prime. This particular "lot" has a thinner fiber that contrasts in color from dark at its base to very light at its tip.
Most of my patches are 12x9", though I do have a couple of 12x15" patches with silver (discontinued) and white fur, respectively. Their orange is very nice for tying smallmouth bass jigs. I've purchased orange, kelly green, pink*, red, fawn, and gray online. Try a Google search to get the "best buy" combination of price, shipping, and handling.
Some of my Darice Craft Fur came from Jo Ann Fabrics. Colors included black, white, and brown.
* - white fibers with very short, pink underfur.
I just look at the length of the fur fibers. If the longest fibers are 3" or so - get it. Some of them have alot of underfur but just got to deal with it. A 9x12 patch cost about $3 at my local shops so it is worth dealing with the under fur. I have several basic colors that are Darice label.... black, white, gray, orange, yellow, kelly green, tan and brown. Have bought it at Michael's, PatCatan's, Wal-Mart and a mom-n-pop local shop..... Cabin Creations.
They carry doll hair also - much longer but have never purchased any. Another brand of fur i have is called Faux Fur that is made by the Fibre Craft company. This fur is much shorter in length but has several different natural colors of fibers in each patch. I cut it off the fabric backing and chop/mix it to create dubbing. A 12x15 patch costs under $4.