I like learning modules for distance learning. One unit, one module. Everything neat and tidy with a clear sequential path that students can follow without too much trouble and then come back and access the material anyway they like.
One problem with Bb9.1 learning modules is that they force discussion boards to open in a new window (there's no alternative, though discussion boards will open in the same window from e.g. a content page). I really don't like this, but Terry Gray of Palomar college doesn't see a problem with it. Anyway, I enjoyed and found useful his video about learning modules.