Chances are that you’ll have to present material. A slide deck can be two things: a visual support for your message during the presentation and a stand-alone record for it that can be distributed.

During the presentation, slides are a visual support helping you to communicate your message and facilitating its memorization. As such, they shouldn’t compete with you, the presenter, who remain the primary conveyor of information. Most people have difficulties reading and listening at the same time, so 
keep your slides simple. Also, simplicity gives the image of clarity, so you’re definitely better off having simple slides.

Once your presentation is over, your slides serve as a record. Your audience should be able to distribute your slide deck to others and these people—who didn’t see you present—should be able to understand it. As such, your deck must be self sufficient. The main success factor to achieve this is to build your presentation in a pyramid, breaking the message with one idea per slide and writing that idea in the tagline of each slide (this approach is called the assertion-evidence structure, see Alley, referenced below).

Irrespective of its primary use, a slide deck should be self sufficient. However, your slide composition depends on their primary use: if you are looking for a visual support only, you will show very few details, leaving those for you to present orally. On the other hand, if its primary use is a stand alone record, you will need to specify these details.

In almost all cases a slide deck serves both purposes and you end up somewhere between these two extremes, but identify clearly what your primary goal is and make sure that the format of your deck supports it.

Understand the two extremes and decide where you need to be. The “Zen” approach is perhaps the best example of the extreme visual support slide design: a photo and, sometimes a key word. On the other hand, the consulting firms have mastered the use of presentations for establishing a record. Just to be clear: as long as the tagline summarizes your slide, either approach is acceptable.The one on the left is from Garr Reynolds. Garr’s approach, as explained on his website: Presentation Zen, uses lots of images and very little text. The communication style is much more emotional than logical. The slide on the right is from the Boston Consulting Group from a presentation to the French government. There are no emotions here, it is entirely geared towards logic. Also, compared to Garr’s slide, the message is much more complex and oriented, no doubt, to an entirely different audience.

These slides are two extremes but both are excellent at what they do. Before you develop your next presentation, think about the primary use for your slide deck and translate this information into directions for developing your slides.

References:

Alley, M., et al. (2006). “How the design of headlines in presentation slides affects audience retention.” Technical communication 
53(2): 225-234.