CloudFlare you get what you pay for. You'll see a pretty high rate of origin pull, which is a metric most people don't look at when comparing CDNs. (i.e. out of every 1000 requests do they refetch from you 1 time or 600 times?)

It might even be disingenuous to call CloudFlare a CDN at all. They are really a web application firewall and app delivery service.