I think bongs get you the highest but not because of the higher THC content. They get you the highest because the smoke is cooled by the water making it easy to take a bigger hit. With a dry piece or a joint/blunt the smoke is often hot and harsh making it difficult to get as much smoke deep into your lungs. A bong is actually less efficient as far as THC content goes because the water actually filters out a small amount of the THC along with the tar and the heat but a bong rip is going to let you inhale MUCH more smoke than a dry pipe or joint will. I think bongs conserve more weed than a joint or blunt because a bong bowl is not burning all the time, but I think a dry pipe conserves even more because it is harder to take bigger hits meaning you are not burning so much weed per hit. But bongs definitely get you more fucked up.