It seems both protocol does the same thing but is there a advantage of one over the other?
You should ask yourself what is important to you (encoding, encryption methods, standardization, etc.)
Jason Schneid wrote an excellent comparison: http://www.internetvideoarchive.com/IVA/news/2012/09/13/progressive-download-vs.-adaptive-bitrate-how-to-choose-the-format-right-for-you