I had to get this straight in my head too. Here's Louis' answer to my same question from months ago:
"The bipole is when the front driver is in phase with the rear driver. They have a very wide soundstage and tend do dissapear in the room. In Bipole the sweet spot in front of the speakers is wider.
The Dipole is when the drivers are out of phase. Both versions will give a greater soundstage and much wider and deeper than monopoles. The dipoles will have a bit more focus and clarity due to the side cancellations or nulls, but the sweet spot is a bit narrower than the Bipole."
If you'd like lots of dipole theory try Linkwitz: http://www.linkwitzlab.com/
From my puny understanding a bipole would simulate a point source that some say would provide perfect imaging and a dipole (because front and back waves cancel each other out as larger/lower frequency signals meet at the sides/top/bottom of the speaker) interact with the room less, but result in severe bass roll off at lower frequencies (perhaps lower than the Super 3 BPC can play anyway).