that's a very interesting question to me!
I faced this topic in for several projects and I've to say that is stil not 100% clear if, as UXs, we have to pay attention to it.
In terms of UX, in my POV, they're slightly different:
* Create an account is more for content available only if you own an account, for instance Dropbox.
* Registration is a hook to provide extra features available only for registered (and logged) users, for instance Ebay.
I never found any report/data able to validate these assumptions.
We decided to follow this approach for marketing reasons. To increase the user engagement we delivered different scenarios for "create" and "register"
I hope it will help