Carroll,
This is not a scientific answer as to why people look down on fiberglass Cobras as compared to aluminum ones, but at the car shows I have been to and talked to all the people, about 90% seem to feel that because the originals were made of aluminum they were stronger, safer, etc because they were race cars. This seems to be a Cobra stgma if that is the correct term as when I point out that Corvettes have always been fiberglass, most people just say, yea but they weren't made to race, they were show room cars. Obvisusly I don't meet the most knowledgeable people at these shows.
Ron