I only have personal experience with San Juan on that list - most of my leisure travel takes me to Europe or Asia, and most of my business travel takes me to far less exciting places.

I stayed at the Marriott Stellaris and walked through the Renaissance there. The atmosphere at the Marriott was definitely more lively/loud because of more bars, more families, and the attached casino. The Ren was a quieter and decidedly more elegant. Per a friend this is the same in Aruba too. Grand Cayman is a much quieter destination overall than either San Juan or Aruba.

I've personally not needed the pampering of the Ritz so couldn't justify the extra $/miles for it, but that depends on what you want to do on your vacation. If you are just looking to relax and be pampered at the hotel then the Ritz is the best option IMO.