as myfish says,flouro does have its advantages ,some disadvantages as well,but it certainly is not invisible underwater. there is an online article by an industry professional that shows the invisibility claims are rubbish.ive posted it on wsf in the past,but as usual the companies producing the stuff either get the articles removed,or fill the net with so many adverts and related cr4p its hard to find negative articles .
where presentation of a bait ,or unrestricted action of a particular lure are required,particularly the smaller soft plastics,i reckon the softer the mono the better,stiff lines such as flourocarbons can inhibit natural movement.
cheers rab