There have been a lot of discussions about this in the Luxury Hotels forum - I would suggest that you do a search there.

To give a different experience from number_6, I used to stay at the Pen regularly, and although the rooms are very good, I found the service to be very disappointing. One of the things that made me cringe was being asked whether this was my first stay with them every time I checked in. When this happens 4 times in a year (and all of the bookings are made by Amex) it makes you wonder... Recent comments about the hotel include that the lobby area often appears to be full of tour groups.

I really like the Ritz-Carlton. Like you did, I stay at the Club floor. I do this because of the highly personalised and warm service rather than the food presentations (I usually just take breakfast there). I prefer the rooms at the Pen, but stay at the R-C because the service for me has been vastly superior, and because they make me feel like a valued guest. They are also extremely responsive to requests and feedback. I will be staying there again next week.