I created a browser based test a few years ago that captures CDN latency from real users and correlates the results regionally using MaxMind (http://cloudharmony.com/speedtest). CDNs set themselves apart outside of the US where infrastructure is more complex and costs are higher. I posted a spreadsheet that provides a breakdown on CDN latency globally based on this testing (tens of thousands of tests from thousands of ISPs):

https://docs.google.com/spreadsheet/ccc?key=0Al_R0WNcU3q9dGV...