As a Leader, the100% Fluoro Leader Material can't be beat for toughness and abrasion resistance.
In general, (and yes, different manufacturers have different specs for each line) there is a big difference between Fluoro leader and Fluoro line material. Most Fluoro Lines are actually copolymer and are sometime softer than mono. Yes, cuda killa is spot on about it sinking. but it isn't much.. the difference in specific gravity (a measure of density) between fluoro line and mono is only a couple hundredths. Flouro line material as a main line probably has more of place as an open water line with no structure around and works well in clear water. I've found it to be more limp than mono... to be clear, this is Fluoro line material, not leader material; It's totally different. Personally, I've known quite a few others that did not like the Line material and choose mono or braid over it as a main line for saltwater use.