Hi Becky,

The major difference between nylon and fluorocarbon comes from the fact that fluorocarbon has greater density. (When sold for fishing purposes it's advertised as sinking line while nylon floats.) Greater density is an advantage to strings because it means greater tone and volume. In practice, they have clearer, richer tone than nylon - sort of like a cross between nylon and steel. They sound great!

Fluorocarbon stretches less so, after the initial break-in period, they remain more stable and in tune than nylon.

Best,
Ray