When evaluating the CDN effectiveness you should take into account the technical characteristics of the network, functionality of CDN and service level.
If you need to evaluate CDN from the technical side, you should think about such parameters as the number of points of presence, peak bandwidth, number of content requests per point of time, latency between the request of content and the beginning of video streaming on device - this parameter becomes more attractive when using CDN.
CDN solution also should help the functionality of video-portal and make communication with internet-audience better. Besides data delivery the professional CDN provider should help in different ways - support several streaming protocols, support transcoding, offer vast number of instruments for monitoring and analysis in real time.
Also it is necessary to understand that CDN effectiveness for business is also determined different way. Connecting to CDN you get the full infrastructure in your disposal that will be used to stream video, as well as give your content streaming tasks to professionals. This allows you to concentrate on solution of main business-tasks and get quality support when you need it.