I can't specifically answer the question, but in my experience the JW Marriotts offer a little "extra" than the regular Marriott properties. Most of my "JW" experience is at the Desert Ridge property in Phoenix, which boasts two very nice golf courses, several on-property dining choices, including a Roy's (which is good, but not great), and a host of other amenities.

In my opinion, these properites fall somewhere between the "regular" Marriotts and a Ritz Carlton, though I would argue that the JW Marriott Desert Ridge is superior to the Ritz Carlton Phoenix.