No problem.
I felt really, really bad not including "the math" supporting the claim, so here's a link to an excellent paper on the topic of drivetrains that explains all of the phenomena. It never specifically addresses the case of the 6 wheel drop, or what happens if you lower the sideways traction of one of your wheel sets (i.e. if you put omnis on one part of your drivetrain) but it shouldn't be too hard to see how a 6 wheel performs better than a regular drivetrain as a result.
If we're engineers, I feel we shouldn't be content with the what without the why...
http://www.chiefdelphi.com/media/papers/1443