My friend Amy made dread rings by rolling Sculpey polymer clay around wooden dowel forms, then sculpting and tooling patterns into them, and then baking them in a toaster oven. I haven't worked with the Bake & Bend clay yet, so I don't know if it's any better for dread rings than the rigid stuff, but the rigid clay has worked just fine for me.
It's a Sulpey product. I used it on my sons mask for teeth and think it's well suited for that. My dread rings were made from it too. But your right, as far as dread rings go, I can't see there being a difference in rigid or rubbery.
If you're good with a dremel/rotary tool, you can go to your local hardware store and buy various couplers for PVC piping, just the plain white stuff you use for irrigation. Draw a design on there with a pencil or pen, dremel them down, sand with a fine grit paper if you want them smooth, paint and BAM, dread rings. I'd suggest 1/2, 3/4 and 1 inch couplers.