If you read the study it seems to make sense, I'm not going to copy and paste it so you'll just have to go click on the link and read it yourself, but it basically just proves how inefficient smoking cannabis is, so we should all learn to eat it

It also sounds like when this test was done, vaporizers weren't as popular as they are now. It would be interesting to test a popular vaporizer, such as the volcano, and see how it fares.

But I think the big reason people say they get higher from a bong than from a pipe is because you take harder and deeper hits with a bong than you do from a pipe. Hit too hard from a pipe and you'll suck down some ash, but a bong, hit as hard as you want and fill every inch of your lungs with some nice cool smoke. That, I think, is why people believe they are getting higher from a bong. I have noticed that I use considerably more bud with a bong than I do with my pipe, so I gotta say this study doesn't sound too far off base.