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

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.