Use CDN or locally stored files?

Question

I know what a DNC is, but I wanted to know some other things about:

• You should choose to use CDN or use locally stored files?
• What are the advantages of using each of the options?
• Which customer benefits the most?

I don’t want your opinion, or how you do it. I want to know what are the advantages (with data proving the same) related to the speed of loading, and distribution, as well as take into account the practicality of maintenance and repair of the option.