RMC Spell Law, on page 38 under Base Attack Table in the right hand column, says that you should select the realm, and then select the column under the realm that applies. It also says that if neither column applies, then you should use the General column.
Therefore, for the base lists of Hybrid spell casters, you should always use the General Column, as their base spells do not fully apply to any individual column. For their Open and/or Closed spell lists, use that column that applies as appropriate, depending on the realm that the list comes from.
