[noelwelsh]

Depends on the situation.

Our product (Myna; mynaweb.com) provides a JS client that our customers embed on their web sites. If we give them a Cloudfront URL we have just created a big legacy problem for ourselves if we ever want to move off Cloudfront (and we did and we have!)

If you're creating a pure JS client connecting to an API on a different domain you have to worry about CORS support to get cross site requests. It's not a huge problem but it slows your site down a bit (you have to make two requests to check CORS permissions and then send data, where you could make one without this issue) and you can't support legacy browsers.

So there are a few reasons why using a Cloudfront URL might not be 100% suitable.