With Shimano disc brakes, there are two options for types of brake pads: resin or metallic. My understanding is that the metallic brakes generally have more stopping power while resin are more modulated and squeal less.
With that said, as far as I have seen, some use a split-pin to stay in place, while others use a bolt.
This is strange to me: I feel less comfortable knowing my ability to stop is based on a bent split-pin rather than a screwed-in bolt! Is there some explanation for this?
My best guess is that the metallic pads create more heat, which could warp threads, but that's just a guess.