Go read what Dr Fish wrote. Then read it again.
I'm not sure about the sink rate - flouro is a little denser than nylon, but 3X the sink rate? I'll have to think about that a while.

But the crux is that flouro material has a refractive index closer to water than nylon does. That means that light passing thru flouro is distorted less than it is thru nylon. Light still reflects off the surface of both, and there is still some distortion passing thru, but IN GENERAL, you can get by with a 1-2X larger size flouro than you can with nylon. Plus, it has much better abrasion resistance.

I swear by it in clear trout lakes and in saltwater where fish have rough mouths. In a bluegill pond, don't know that I'd go to the extra expense.