Now that's a good answer! Now I won't go astray.Stainless has a lower thermal conductivity than titanium - not by a huge margin, but it's there. I expect that the main reason that stainless is not used for brake pad heat shields is that it's springy and it really doesn't enjoy being flat. On the other hand, if titanium is flat, it's really flat and it stays flat. When it's flat, it can't contribute to pad knockback. Stainless, being springy, can warp, and if it does, it will push the pistons back a bit when the brake pedal is released and that'll soften up the brake pedal. So, titanium wins.