Fluorocarbon line has recently become a very popular option for anglers. It is one of the more advanced types of line due to its physical properties and characteristics. Because fluorocarbon molecules are extremely tightly packed, the line itself is dense. It is extruded in a single strand method, and therefore offers very little flex. Thus it is extremely sensitive, allowing anglers to feel every little nibble.
The best benefit for spin casting with fluorocarbon line is that fluoro has a very low visibility underwater. It is nearly invisible to fish, and does not distort light passing through. Fluorocarbon has almost the same refractive index as water. This is a huge benefit for when fishing clear water and when targeting fish which are spooked easily.
Flouro is also very abrasion resistant, therefore it is a good option for when casting in areas with rocks and juts. Because fluorocarbon does not flex, it has great hooking power for solid hook sets.
However the trade off is that due to its dense characteristics, it holds line memory and will have a tendency to birdsnest. fluorocarbon line has a rapid sink rate, therefore it is great for throwing lures which require deep waters or pinning your bait along the bottom from a weightless presentation. However, it would not fair well with mid to top water lures that you want suspended in the water column.
There is a certain method to tying knots with fluorocarbon, before you finish cinching your knot, make sure you wet your line otherwise the knot is guaranteed to fail.
Fluorocarbon makes up about a quarter of the market, however it is roughly 50% more expensive than Monofilament.
Monofilament is typically the most affordable line out of the 3 categories. Monofilament line provides stretch, which is good for fighting fish. However this stretch means bites are not quite as detectable compared to using fluorocarbon or braided. Mono however retains very good knot strength, it also floats which provides good characteristics for mending or throwing top water lures as well as float fishing. Do keep in mind that mono deteriorates with exposure to UV light. However Monofilament is the most widely used line as it is suitable for a wide range of species.