I'm reluctant to bring up the subject but I really feel uninformed. I started fly fishing over 60 years ago when my Shakespeare Wonderod was the state of the art. I still have it and my old bamboo Phillipson. My question is what are the physical differences in today's composite rods? I'm not looking for how well they work. I'd really like to know what are the differences in design properties like tapers, etc. Why does a new $500 rod cast better than a $100 version? I know there will be a difference in material quality and cosmetic esthetics but what are the Design Differences? Thanks