They'll provide better lure contact during retrieve and better slack line control for hooksets and fighting fish. I am casting to a specific target and only working my bait for about 2 feet past the target. This allows me to make a lot more casts in each tournament allowing me to cover much more water than my competition. A magnetic cast system uses a magnetic field to control the rotating aluminum spool's speed during the cast. A dial moves magnets in or out to increase or decrease braking force.
Magnetic systems provide the most force so are a good choice for less experienced anglers.
Centrifugal cast control provides less overall influence on spool speed, thus requires greater control by the angler, especially if brakes are turned completely off. In experienced hands, centrifugal is the more versatile system. However, Quantum's new ACS system combines the best of both worlds - a high performance centrifugal system that adjusts externally with the turn of a dial. Let your personal preference and experience determine your choice. It allows me to set the spool very loose to pitch the bait effortlessly.