B) might work just fine, most of the time, for the lucky and patient, but it will always be slower.
A) is MUCH better as the nodes contain Meristematic tissue, plant cells that can become branch, flower or even ROOT cell tissue! crazy! Branching Nodes are where the action happens and a buried node will start forming roots from theses cells that were yet to become branch cells.
A. Bury the nodes!
wiki: meristem is the tissue in most plants containing undifferentiated cells, found in zones of the plant where growth can take place. Meristematic cells give rise to various organs of a plant and are responsible for growth. Differentiated plant cells generally cannot divide or produce cells of a different type.