If you want to present slides to fellow students or co-workers, which productivity software should you use to create them?

Use powerpoint. In many high schools you can take an information technology class where you get certified in Microsoft Word, Powerpoint, and Excel. Alternitavely you could use Apple's 'keynote'

When it comes to presentations, my choice would be a Prezi. They are amazing and better than Power Point. Everyone's using a Power Point these days, so Prezi would be unique. Graphics and Animations on the Prezi are better than Power Point. 

The final choice is yours. Go with whatever feels convenient and better for you. 

Hope this helps! :D