We use a cable specially designed for jewelry applications. This stringing material is made of 49 tiny strands of steel. Pic to left shows 7 x 7 cross section of cable. The cable has a plastic coating to minimize any chance of fraying. The combination of flexibility and strength make it, in our opinion, the best choice.
A decade or so ago, the best stringing cable available was called 'tiger tail'. It was made of 7 or so strands of steel. Although tiger tail is strong, it is also brittle and prone to kinking. Tiger tail is still used by many, because of it's cheaper cost.
When jewelry breaks, it almost always breaks at the end near the clasp. We have a special 'torture chamber' set up in our shop to intentionally destroy our work. This way we can find the find the most durable clasping procedures.
We have found the strongest cable-to-clasp attachment to be either two brass crimp beads on each end, (See section of gemstone anklet below), or a doubled-over sterling crimp bead which is then flattened depending on the size of the bead cable. We use solid sterling silver or solid brass for the clasp and end-ring. Some of our designs call for the clasps to have an antiqued finish.