Differences in Presentation Types

What are the pros and cons of all the different presentation types(beamer, ioslides, etc)? I'm looking to make my first presentation using RMarkdown but wanted to know more about the differences.

So far it just seems like the difference is knitting to HTML or PDF but there has to be more to it than that.

As far as I know, there is nothing special about any of them. The only difference is visual. For example, beamer has a very distinctive look and is very common among mathematicians.

Other than that, with RMarkdown most of the time you can knit to HTML, slides, and/or PDF (sometimes even to Microsoft Word).