We use brass only. It lasts longer, and crystals are heavy enough that the fastening matters. After years of trial and error we dropped several types and now work with four: classic clips in polished brass or nickel-plated brass, from 9 to 18 mm, decorated clips in the same finishes, pins, and hand-made binding with thin, flexible brass wire.
Clips go into the hole of the crystal and are closed by fingers or a special tool, depending on size. Binding is slower. The wire is cut to an exact length, calculated from the width of the crystals and the distance we want between them. Special nippers lead it through the holes, and circular motions fix it. The leftover is cut off. The shorter the leftover, the better the hand. For a craftsperson, that offcut tells the whole story.