For most of us, text simply conveys content. Typically, we don't think about the design of the letters we are looking at, but even the font on your opening screen for your prezi sends a subconscious message to your audience. They will perceive this message in just a few seconds. Take a look at the fonts in the following image and see for yourself:
Your choice of fonts set the scene for your presentation.
No matter which set of fonts you end up choosing, make sure the body text is easy to read, and don't write too much. It is best to stick to short titles and subtitles, and small amounts of body text.