Pros & Cons of vacuum vs. mechanical secondaries?

Vacuum secondaries can be set to just about any camshaft unless you're going solid roller or huge flat tappet. I love vacuum secondaries for the street when working properly they're a thing of beauty like a six pack, I've also run mechanical secondaries with great luck especially with high rear end ratios which allows the motor to rev quickly and adjust to quick air changes better. Then you have carbs like a Carter Thermo which controls the air with a air door that's weighted. Sizes important more so with mechanical secondaries. Either can be made to work. For speed cars are more forgiving especially with high gear ratios.