I always thought vaping bud was the most efficient because you can vape the buds then cook with whats left. I don't know the exact chemistry behind it but it goes something like this: vaporizers only vape off the THC in the cannabis. Cannabis contains serveral other phsychoactive chemicals such as CBN and CBD. With the leftover vaped bud you can make brownies or other food snacks and still experience a good high from them. Essentially, you get to use the weed twice! Sounds pretty efficient to me.