Well...both acids can cause bitterness, but alpha acids are around 9 times stronger than beta acids. Because of this, beta acids aren't really concidered for their bittering flavor, more for their bittering aroma. Most aroma hops tend to be higher in beta acids, which results in a better smell.
He who drinks beer sleeps well. He who sleeps well cannot sin. He who does not sin goes to heaven.
Another HERMS rig...