Well it's silly to assume that these are mutually exclusive methods of teaching. As you well point out, prepared material on a computer can show things that you

Well it's silly to assume that these are mutually exclusive methods of teaching. As you well point out, prepared material on a computer can show things that you simply can't on a blackboard, things like visualisations, graphs, schematics, or other things that are either too tedious or impossible to write down on a blackboard and copy to a page. My rule of thumb is: screen for exposition, blackboard for problem-solving.