This is strictly my opinion on this subject and for bass only.
Fiberglass is old technology that the stubborn generation are use to using and wont change. The newer graphite rods, i.e. "Crankbait rods" are far superior to glass in weight of rod and the newer ones have just as good of actions or better. IMO glass rods for the bass fisherman will be gone in 10 years, we younger guys just have to show the light to the stubborn generation that wont change.
Like anything else that is new, it takes time. When the graphite rods for cranks first came out. Yeah I believe that the glass was still better. But with R&D the graphite is now far superier.
You guys that are die hard glass rod fisherman should try a "crankbait rod" or Loomis Popping Rod.
You might be suprised. Great action with alot less the weight. 8-)