I've been to both the Marriott's on the Cayman Island (the Marriott resort and the RC.) Hands down the RC is a major step up in luxury. I'd expect that to be the case in most locations that have both a Marriott resort and an RC resort. If you want to "step it up a notch", I'd look at the RC options.

But there are some other things that could affect your decisions. Are planning on traveling alone? With a spouse? kids? friends? For example, if you are traveling with the whole family, someplace with suites might be more helpful (i.e. St. Kitts has a Marriott timeshare on the property with the hotel and it is possible to find 1, 2 and sometimes even 3 bedroom properties for very reasonable point awards.)