This question has been on other discussion threads as I was in the same situation last year in December. We ended up booking the Renaissance because it was my husband's 60th birthday and I wanted to go to "The Pearl" restaurant in the hotel. The Renaissance and Marriott Stellaris are basically on the same beach and relatively close to each other so that will probably not sway you either way. I will say that I booked a city-view suite hoping to get upgraded with Platinum status but that did not happen, so we did not get to see the ocean from our room. The view was great from the restaurant though. The hotel said they were booked full and would not grant an upgrade to ocean-view room. I went with booking the city-view because it was more or less "off season" so to speak for cruising and figured I had a good chance at the upgrade. I am not sure if actual Marriott would be or would have been more accommodating than Renaissance. I haven't actually stayed at that many Renaissance properties. The hotel was clean and the room was sufficient. The staff was very friendly so I had no problems with the property except for the fact I did not receive an upgrade. The city view is not much to speak of in that area.
I hope this was somewhat helpful. You can probably find the old thread somewhere within the discussions around September or October, 2012.
Thank you so much for your response, madmax. I am thinking we should go with La Concha, but am kind of playing with the idea of the Ritz-Carlton. Having to be guided by the reviews on Trip Advisor so that's always hard. I'm also toying with the idea of catching a flight to the USVI for a few days, or perhaps a cruise out of San Juan. Sometimes I think it would be so much easier to go back to the olden days of relying on a travel agent. hahaha