Thanks Geedix (cool avatar!) and Jack for the replies, very helpful stuff. I'm glad to finally start posting, I've been using GSAP since it first came out for Flash back in the day and never stopped!
To confirm, will it be enough for me to ask who the ad network is serving the ads? Is that the correct way to frame the question to determine which CDN is appropriate for a hypothetical banner build?
Is DoubleClick considered the ad network? If so then I would use the Google CDN links.
My understanding is that the publisher network are the sites that are ultimately displaying the ad content? They wouldn't matter in terms of what is cached on the end users' browser right?
Sorry for making my questions so specific! I think I'm getting it now, again thank you both so much.