Jac747, I'd encouurage you to choose either the original RC or the FS if you're planning to do any shopping, or more specifically if you plan to do any walking to/from the hotel. The FS and original Ritz are both in very pleasant areas when you step outside the front door, and both are in the midst of excellent shopping. The BC Ritz is in a particularly unwelcoming area (not necessarily unsafe, but certainly unwelcoming) when you step outside the front door, and the closest interesting shopping is several blocks away -- in the direction of the other two hotels.

Considering the original RC and FS, both are very good hotels, though neither would get a World Class mention. Choosing between them, it's not a burden to stay at either one. The RC has more of a patrician, old Boston feel (some might describe it as stuffy), while the FS has a more contemporary feel. My preference is for the FS, but others find that the RC has more character and a sense of history.