I faced this same question in deciding where to have a 5 night award stay in September. While I usually don't need luxury, like to save money/points, and thus would have chosen the Sheraton, I sprang for the St. Regis for its location. Sounds like I made the right decision.
BTW, if you're transferring any of your Starpoints on this trip into airline miles, the Nights & Flights II award makes the St. Regis much more affordable on a point basis. A 5 night stay is normally 50,000 points (10,000/night), available at the Fifth Night Free rate for 40,000 points (8000/night), but with N&FII effectively is 30,000 points (6000/night). You pay 70,000 points total, 40,000 gets transferred into 50,000 miles on the airline of your choice, then you get 5 nights for the remaining 30,000 points.