ive always used steel baffled exuast cuz they dont wear out like fiberglass iwas told a long time ago that once the fiberglass blows out it actually causes turbulance in the exuast so other than weight and cost what is the advantage of having fiber glass?

 

cheaper and easier to work with plus it suppresses exhaust pulse better

 

You just mentioned to the two biggest things every manufacturer and every rider is aiming for.. Cheaper and lighter.

The fiberglass on a quality muffler doesnt blow out.Most mufflers will "burn in". but the fiberglass remains for a long . long. long time. they do get louder as time goes one, but thats only as the fiberglass becomes more compact and its ability to asorb sound lessens. this doesnt affect the performance of the exhaust.