I'd say its different for every car
Cam gears do give you a lot more options with tuning and your powerband, such as:
Advancing Intake and Exhaust: This will provide the car with more bottom end power, and will decrease top end. Advancing both cam gears will move overlap earlier but will not increase it.
Retarding Intake and Exhaust: This will increase the cars top end, but will decrease low end. Retarding both cam gears will move the overlap later and but will not change the amount of overlap.
Advance Exhaust Only: This will help the cars top end, and it reduces overlap.
Retard Exhaust only: This will help the cars mid range power, very useful for cars with big turbos / big cams. By increasing overlap, It decreases lag significantly. Doing this will bring the boost on all at once.
Advance Intake only: This will increase overlap and helps the cars bottom end and mid range power. This mod will bring the turbo on all at once.