“ Fluorocarbon line looks a lot like mono. But it’s a different material, and transmits vibrations much better. A lot of fishermen believe that fluorocarbon is more sensitive because it has less stretch than mono, but according to the good folks at Stren, that isn’t the case. My good friend Eric Naig at Berkley says that all nylon monofilament contains 18 to 35 percent stretch, while most fluorocarbon contains 28 to 38 percent. And stretch in braided line is in the 2 to 7 percent range. The difference is that nylon has a stretch recovery, or rubber band effect. Fluorocarbon may elongate, but differently. Actually the density of the line is what makes it more sensitive." -Bill Dance
"Now, Bill confirms the density aspect of fluorocarbon, and its applicability to creating a better feel. However, he is righting a wrong here by telling aspiring anglers that in the marketing of this line there has been a misconception. I applaud Bill’s integrity here, and expect nothing less from this indisputable fishing icon. While fluorocarbon may be marketed as being low in stretch, it actually stretches more than monofilament." -John Warren
The above was taken from this blog article. Very interesting read.
http://fishingwithconfidence.net/fluorocarbon.html