As Skip asked, it is more dependant on the water you will be fishing at a given time...most fishing on the Upper Bay will allow you to get by with a mono leader since the water will be cloudy or dirtier looking...cleaner, clear water will warrant a need for the flourocarbon leader...another note - when using flouro as a leader, use "leader" material not regular flouro line as the leader...leader material will be a little stronger and alot more abrasion resistant which you will want when fishing around structure.