I go to a great conference (Analytical Genetics) where only whiteboards are provided - no Powerpoints or transparencies are allowed. The dynamics of the presentations are wonderful, and taught me the importance of body movement in teaching.
With a white- or blackboard, the observer's eyes are led directly from the body - arm - hand of the person creating the visuals to the visuals themselves. The visuals are an extension of the person. This helps the observer form a mental connection to what is being drawn, because our brains are much better at attending to people than to abstractions.
In contrast, with any kind of projection, the presenter and the visuals have no physical connection. Using a stick pointer rather than a laser pointer helps, as the stick leads the eye from the presenter's arm to the part of the graphic being described.
Watching the visuals being created is also a big help for the learner. So writing on the board or overhead is better than showing a finished graphic or table or notes. Similarly, gradually assembling a complex image in sequential Powerpoint slides or an animation is better than just showing the final graphic.