Pros & Cons of vacuum vs. mechanical secondaries?

Whatever carb or efi your used too and comfortable tuning.

I've only tuned a mechanical once, the 650 Quick Fuel I have now. I think VS are more forgiving. My biggest problem is lack of tuning information, as in accurate consistency. Seems there is 10 different way to tune them and deciphering which is the correct way can be a real pain for a daily driver.