I've heard that the rubber lines will stretch but the teflon / stainless braided ones can break suddenly, making the rubber ones more reliable but give slightly less performance because they stretch a bit under hard braking. My SD can lock up its tires in a panic stop, so this is an area I don't want to mess with. I'm not one to check brake lines weekly, although the braided stainless is admittedly way cool looking.
Robert W. Roe
1984 300SD 169K mi