I have both a brass assortment from Nordstrom (courtesy of my wife) and mother of pearl (courtesy of my extensive Carlo Franco selection). Â I like both. Â The Nordstrom brass have blunt, not pointed ends, which might be a factor, but my shirts have not been damaged by the metal. Â Still, I normall stick with the mother of pearl these days. Â I realize it is an indulgence of the most extreme variety, but I'd love to have a silver set for special occasions. Oddly enough, but for whatever reason I've never laundered any of my nice collar stays, only plastic ones.
I, too, am a recent convert to the MOP stays; I quite like them. I have a couple of pairs in sterling (from Links and Dunhill), though I'm not a big fan; they seem to bend too easily.