SS brake lines don't expand and contract under the pressue of the brake fluid like rubber lines do. More of the pressue is applied to the pads, and the stiffer lines allow for more feedback to travel up them and into your controls. This feedback provides you with a feel for how the brakes are performing in the palm of your hand, not simply the feeling of slowing down.
Brakes feel and perform better, and stopping is a pretty big deal
