Are you using mono, fluoro, braided leaders or a combo.
I'm a mono fan, while holding that fluoro does have it's time and place.
- I think the invisibility part is B.S.
- Regarding advantages and disadvantages, it goes something like this: Mono is more supple, and hence better for drag control. It has less memory, which makes fishing easier. Mono stretches more, which is like having a soft rod tip to absorb energy and protect tippets when a fish runs. It also degrades in UV light, which means when you drop that tag end you just cut off, or break a fish off, it won't be there 200 years into the future.
Fluoro has superior abrasion resistance. So if you are bottom bouncing on sharper rocks it does not weaken so quickly. It also does not break so easily when fish teeth rub against it. Fluoro does not soak up water, so after hours of fishing 5x is still 5x and doesn't turn into the diameter of 4x or 3x. Fluoro does not degrade in UV light, so that ancient spool in your pocket is still good. Fluoro does not stretch, which can be good for harder hooksets, and some say it allows more direct feel between you and what's on the other end.
Fluoro generally has a higher strength/diameter ratio. On the other hand, due to the stretch of mono, a sudden head shake or run will put less stress on mono, and in use many say it's stronger. And on the other hand, poor abrasion resistance of mono may mean it has more knicks in it and thus lowers it's strength.
Most of my fishing is smaller trout where drag is the enemy, hence my preference for mono, and more supple mono's at that. Don't get me wrong, though, if chasing trophy fish with their bigger teeth, or toothy saltwater fish, or if you're really dredging the rocks, fluoro has it's place. And, if you value that abrasion resistance AND still want the stretch, you can do that, just build the leader out of mono and use a fluoro tippet, but you still lose the micro drag control of a mono tippet.