Im goin with Edgar, if you think joints are wasteful you arnt rolling them right.
Think of all the resin that builds up on bowls and bongs, that right there is waste. With joints you're smoking from tip to end, the smoke is filtered by the remaining bud which is also eventually smoked.
When you smoke a bowl you are constantly applying flame to it, more flame is more heat which is more THC being destroyed. Joints on the other hand you should only have to light once, when you arn't hitting it somebody else should be and even when nobody is hitting it there is only a small trail of smoke rising.
The last hits are the best, and anything that remains can be re-rolled.

The study testing seven smoking devices can be found here: http://www.maps.org/news-letters/v06n3/06359mj1.html