leader question

From what I gather a lot of anglers are using fluoracarbon (sp)
leaders. I use power pro and like to use hard and soft baits. I could
see where such a leader would help on the use of soft baits. The bait
would likely move more freely and the line would be less visible to a
fish contemplating a strike. As for hardbaits I don't know if the
leader effects the action. The strike is more of a reaction strike and
the visibility of the line may be of lesser importance. Those are my
own naive perceptions but I am looking for something a little more
definitive.