35mm slides are best suited for use in venues with controlled lighting. They allow the speaker clean, smooth-flowing presentation visuals. With a remote slide advance control, the speaker presents virtually hands-free.
Audiences give their full attention to the presenter's words and visuals.
Overhead transparencies are best suited for use in venues where the audience will be asked to take notes or participate during the presentation. Often the presenter has no control over the level of light in the room, making the use of overheads more suitable than 35mm slides. Overheads in mounts can be bulky, especially if the presentation contains a large number of visuals. On overheads colors are not as vibrant and text is not as crisp due to the lower resolution available on a color printer. Consider your presentation venue and audience and select the medium which suits it best.