I did a five-night stay at the Westin GC this summer, and I also walked around the Marriott and the Ritz.
I echo Canada101's comments. The Westin is a better place to stay since the property is on the beach and has more beach-facing and beach-front rooms. The Ritz, physically, is a nicer hotel, but that is not as relevant here as it is elsewhere, given the beach.
Also, the beach is wider at the Westin than at most other places along the beach. The beach is absolutely cramped by the Marriott. I walked a few miles up and down the beach, and when walking by the Marriott, the chairs set up for the Marriott folks basically occupied the entire beach, and I think the Ritz wasn't much better, whereas at the Westin, there was plenty of space beyond the chairs.
Agree that the restaurants are expensive. I ate a lot for breakfast, skipped lunch, and ate dinner off-site.

Elite recognition could use some improvement. At check-in, the person was initially not going to give me the best available room, and was not going to do anything for me (a Plat) regarding alternative amenities given the resort fee.
After spending 15-20 minutes at check-in and talking to a manager, I ultimately got what I was entitled to -- to be clear, nothing beyond what I was entitled to, just what I was entitled to.
Regarding the room, there was a beach-front room (where I could walk out the door of my patio onto the beach) that they weren't going to give me. I think the issue there was that the room had two beds whereas my original booking was for a king. Still, they never mentioned it until I repeatedly insisted such a room was available and pulled it up on a computer in the lobby.
Regarding the resort fee, their practice is to give plats who want to do breakfast the full continental breakfast as the make-good on the resort fee. The person who checked me in simply wasn't trained.

I enjoyed my stay, but there is absolutely no way that I would spend peak-period money for a room at any of the properties. Off-peak, it's a good deal.