What is the difference between Art Clay Silver and Precious Metal Clay? Really they are basically the same material. However, they are enough chemically different that you cannot combine them in one project. You can use the same methods on both materials, and the same tools, but you cannot use them together.
Art Clay Silver and Precious Metal Clay are made by two different companies. Precious Metal Clay was produced first and in order for Art Clay Silver to not run into the patent for PMC, Art Clay Silver had to made differently enough that they are not compatible.
So, go ahead and buy either one, but don't use them together. Art Clay Silver makes many great books on how to use Art Clay Silver, but a lot of them are in Japanese, so you need to be able to interpret them.