bredman

You bring up a good point. For stuff like this where the resource is plausibly already loaded before the user ever even visits your site you may want to look at what version of this library your users are most likely to have preloaded.

You probably want to devise a scoring function based on likelihood that the resource is loaded already and cost if it is not and rank your CDN options based on that.

I'm actually not sure where the data for this site is coming from (there's some mention of Pingdom on the about page) but CDN performance can vary significantly based on user location. For that reason the only CDN comparisons I really trust are ones that are taken from end-user computers of a representative sample of the viewer you're trying to optimize for.

In this case if this data is from Pingdom monitoring locations it's particularly bad for estimating performance for a JS library that's likely loaded by end-users who are not browsing the web from well connected data centers.

Agreed that the look is nice and admittedly in the absence of other data I would probably trust this data.

One option would be to use Route 53 weighted round robin (WRR) DNS records and health checks to accomplish this.